Wow! I wasn't expecting anything like this video turned out to be. I feel like I just subscribed to a class and I'm about to be a certified home technician. Good stuff! Very impressed with your work and when you through it on the white board, I was blown away! Keep up the great content! Thank you for your time
OUTSTANDING!!! I personally appreciated the professional approach and clear explanation of the electrical issues a automobile might have. Great learnig.experience. THANK YOU.
Hello Just wanted to say that i am blessed to see any of your videos!! You made a huge impact on me and gave me knowledge that most people will not do!!!! Thank you so much sir!!!!
That is a great question! One way is to look at some of the other sensors wire colors. Grounds are typically shared between sensors. Also if I see a 5-0-0 sensor I will jump the ref. to the signal using a 5kohm resistor and watch scan data signal for 5 volts. If you use the resistor and jump the ground by mistake = no harm, no foul. DO NOT do this without a resistor if you don't know which is which
Thank you very much. It is hard to ignore the negatives. I just need to remember that I don't need to always defend myself. I have always let me work speak for me. It was really cool of you to defend me over there. I truly am grateful.
As an instructor your a natural communicator. The information you provide is priceless. I do wonder if your students absorb the info considering all the variables to every circuit design by manufacturer. I wonder if its possible to be a general service technician at all or do we train techs to specialize entirely on the electrical diagnostic side of the business only and some on the mechanical side of the business.
Thank you! Great video it helped solve my issue with emission monitors not being ready. The aftermarket fuel pump had the 5V Ref and PCM signals swapped at pigtail. After I swapped the pins on 8 pin connector I got 2.7 V where before I was getting 4.07. I wonder how many fuel pumps were delivered with that quality issue. Thanks to this video I was able to get 2002 Mustang to pass CA smog.👍🏽👍🏽
I was also wondering about the question below (everxxxx), about possibly jumping the 5v ref to a shorted signal wire and causing damage. Would also like to recommend Paul's book, explains things well and if you're still not sure about something he always responds to emails to your questions. Top guy!
@Bonfield2002 Thank you very much for the compliment. I always tell my students that it will take years to absorb all of the info I pound into them with my class. This is why I created this "field manual" (my book) for them to take with them in the field. It is the one book they will want to keep in their toolbox!
The previous post, I accidentally wrote batterias. I hit send before I was completed with my response. Sorry about that. By the way great videos with a lot of very useful information. Thanks
That's what I'm talking about! When you start to understand bias voltage and how to use it, it will change how you troubleshoot opens and shorts in wiring harnesses.
You are correct my friend. This is why I did another video. I called it "Signal Circuit Integrity Testing Update for my eBook" Also Section 10 in my eBook "Signal Circuit Integrity Testing" I have addressed this issue. Thanks!
Hi Paul I am fairly new to troubleshooting cars.I just watched the video that you and Eric did on misfire.It was awesome as usual. Some of the comments are proof that how many people do not appreciate your level of skills and understanding of Automotive electronic and computer diagnostic.I mean try to explain what an ATTENUATOR is to Joe the muffler man .Please ignore the negatives an focus on positives which are way more as I read. Keep on the fabulous job that you are doing.Thank you
NOT ONE TAKES ABOUT, Other Reasons Why You Get Po452 code. I have a 2004 Silverado that sat for along time. I removed the fuel pump assembly, empty the tank, wipe clean and reinstalled all. Tried to start engine, it would crank, but hot start. Sprayed starter fuel into intake and it would start then die when starter fuel ran out. When to Auto Zone and paid $140 (Refundable if returned in 90 days) and found I had a P0452 code. I kept thinking it had to do with the opening of the fuel tank. Finely (After watching hours of videos) decided to remove fuel pump system. Cleaned opening and o-ring making sure o-ring was in the slot. After installing fuel system, noticed o-ring had come out, moved back into the groove, installed ring, and all connectors. After cranking 2 times, fired right up. All side remember hearing that if the gas cap was not tight or was leaking can cause the same problem. I wanted to pass along since I did not find a single video taking about the solution of a lose of pressure or a failed gas cap under P0452 code.
Thank you very much for this video, man. I have difficulties understanding lessons but you made it very clear for me to understand, a little quick here and there but great work non the less! My 2001 Z28 Camaro has a P0452 Engine light and I will test it tomorrow to confirm it's a sensor, thank you very much once again for the video!
This is great, I've been fighting a P0451 & intermittent P0452 codes on my Escape. I'm going to do this test tonight to confirm my sensor is good or not. I'm a subscriber after this video!
There will be current flow but it is even lower than you stated as it is a 5v source not 12. In fact the sensor itself pulls this "bias" voltage to almost ground at times. So there is absolutely no danger in doing this test. Also the internal resistor may be even higher ohms than I stated.
This is a great video, but you said never short the 5v reference to ground or computer damage can happen. but if the you are jumping the 5v to signal to see cicuit integrity of signal wire, and lets say the signal wire was shorted to ground seems like that can cause internal damage to computer. The reason I asked because 0v in the scan tool can be caused by a short or open in signall wire. not trying to judge the video maybe something I am missing. I have your E-Book and its great.
No! You wouldn't want to put direct 12v into the O2 signal wire. There is some protection inside the PCM for the O2 signal circuit. I just wouldn't jump direct 12v to it. Use your body as the resistor and do it that way.
@ScannerDanner leave the PCM plugged in, make sure your ohmmeter is reading in the kilo ohms or that it's just not reading zero. And no the ohmmeter will not hurt the PCM on this test.
The kid snoring in class will be the tech at the Chrysler stealership who replaces a gas cap 3 times for an evap leak, when it really there was a cigarette-sized hole in the purge line caused by rubbing against the ECU harness (COUGH THIS HAPPENED TO MY CUSTOMER). The passionate tech's will prevail.
I done this same test on a car at work the other day, but it had a FTP sensor performance code. If you touched the top of the sensor the voltage pid on the tech 2 would go nuts.
@jtech23 LOL you caught that! This poor kid has sleep apnea and he was sitting right next to the camera. Did you see my face when that happened. It was kind of funny. He is really trying, I don't fault him.
@EVERXXXX You could certainly do that, however in my experience a shorted reference circuit almost always comes back to life after fixing the short so I'm not to concerned about it.
I have watched this three times and I got it the first time. Great information but most techs can't do that. I have one question though: Why not just replace the sensor? I do have a scan tool but I guess the stealership does not. They replaced the fuel pump under warranty and a couple of days later the car will not start. I have an Innova 3040c and P0452 is what it told. The stealership told me that I needed new spark plugs that cost $505. I went down to the stealership and observed the plugs.(not an old car). The plugs were fine. Not my first car. I priced out the part and it is $33 plus tax. Look where it is located though. I appreciate what you are putting out there for facts. There can be so many other things wrong with an EVAP low fail. I have 0 degrees F here with a twenty mile an hour west wind. I know what I can do but that is why I have four vehicles. You would think that the stealership would take some ownership on their warranties. I hate to be at 75% operational. It is Minnesota though and I only have one non-heated garage for cars/trucks. You have to get the vehicle in the garage first though.
@ScannerDanner If you check the signal wire for a short to ground you would have to unplug the PCM for a proper test and we want to avoid that step if possible. I suppose you could.....
Hello Mr Danner Thanks for this information My question is about jumping 5 v reference to signal wire. What if the signal wire was shorted to ground but you jumped 5 v reference to signal wire. Is that same as jumping 5 volt reference wire to signal wire to ground wire in the bottom
you mention here dont jum 5v ref to ground,that means with jumper wire or testlight,but if i want to check 5v ref voltage with multimeter,i can do that? one lead to 5v ref ,other to ground,scale on 20v DC. its dwont hurt that regulator?
2006 Chevy Optra (p0454, then p0452) - this is the same car as Suzuki Forenza/Reno(USA) Hello Paul, I have followed your Video instructions and below are the tests i have performed on the FTPS problem so far. I am a DIY'er and seem to have hit a block in the road. I have no wiring diagram for this cars FTPS circuit as i cannot find one. I have a service manual for a 2004 Optra and it doesn't list anything for the FTPS circuit or ECM pin layouts NOTE: I do not have a Fancy dancy scanner with square waves etc. I only have a simple Actron scanner CP9580a and a DMM and test light. Here is what i have diagnosed so far: (( CONNECTOR UNPLUGGED )) With Key off ------------------- 1.) I have continutity on the ground wire(black) With Key on Engine off ---------------------------------- 2.) 5Volt Reference - tested 4.99V on the reference wire (gray) 3.) Signal Wire - jumped 5Vref to signal and backprobed the signal wire (ecm side of connector). Test showed 4.99v proving no connector fault. (( CONNECTOR PLUGGED BACK IN )) 4.) FTPS test - removed FTPS from Fuel Tank Pump assembly and applied -10kpa vacuum on the sensor and it ranged from 1.3v - 4.74v After releasing the vacuum pressure voltage returns to 1.3v ,,,,Did test 2 or 3 times to verify. 5.) Purge Valve - removed from car and applied voltage to test valve open close operation while applying vacuum - Valve opens. Also listened to the purge duty cycle with stethascope and valve was rattling away. 6.) Vent valve - removed from car and applied voltage to test valve open close operation while blowing thru it - Valve closes. 7.) Gas cap is brand new. 8.) The Drive Test Diagnosis - The MIL IS ON !!!...... After resetting MIL and now 93km later the "Evap Drive Cycle Monitor" is complete and "DTC P0454 is confirmed". P0452 hasn't reappeared as yet, but rest assured it will as i have done this a few times already over past year. With the DMM connected to ground and backprobed to the signal wire on connector (ecm side) i observed the Voltage reading while driving for 15 minutes. At very low load The signal was perfect (1.4V-3.1V). Went home let car cool and retested. Drove same distance never tromping on throttle. Stopped, waited a few minutes and restarted car and the MIL went off (expected). All the drive time the FTPS signal Voltage was perfect and MIL went off. SO I APPLIED SOME FORCE TO HER ON THE NEXT TRIP FLOORING THE GAS PEDAL WHILE OBSERVING THE DMM VOLTAGE and sure enough the voltage dropped below threshhold and went haywire at times. This resulted in the MIL coming back on IMMEDIATELY after the second attempt. I am almost sure that the code is being set when there is positive pressure in tank, because freeze frame data indicates PURGE % = 0. Below .1 Volts i think is the threshhold which has to happen on 2 consecutive trips for the MIL to come back on and my testing confirmed that. But i have reservations about going out and replacing the sensor (throwing money at parts) until am absolutely sure about the fix. 9.) Commanded the Vent valve closed with my scanner and applied .5 psi shop air from the evap hose before the purge valve. Everthing seemed to hold pressure but i have no way of determining this as I dont have a fancy smoke machine with pressure gage). So i attached a balloon to the Vent Solenoid end of EVAP system and waited 10 minutes. Came back and the balloon was still holding all pressure, so it seems that i have no leaks, thus no leak codes....dah!! PAUL PLEASE ADVISE, AS I AM NOT SURE WHICH FORK IN THE ROAD TO TAKE FOR THE NEXT STEP. I dont have a wiring diagram showing the FTPS circuit nor do i have a pin layout of the ECM to do a short / open testing on the REF & signal wires. You mentioned in your video not to worry about ground wire in this case and it makes sense. If anyone has the FTPS wiring diagram and ECM pin layout i would be forever grateful as i cannot find them anywhere on the WWW. Whats really puzzling is that I have a 2004 Optra Service Manual but it doesn't show any information regarding the FTPS. PS> I LOVE YOUR VIDEOS - YOU ARE THE BEST TEACHER OUT THERE BAR NONE !!! .....well maybe the legend scotty K.
So, in the top example at frame 16:46, you say that jumping the 5v reference to ground will fry the pcm regulator. If i'm following what you are saying, why would they make an expensive pcm so vulnerable to a short to ground?
I am trying to learn about vehicles and your instructions are very easy to understand. As someone that is now beginning where should I start. How do I get a hold of the circuit
Start with my classes I offer on my website! I have over 400 hrs of training material available for $11 a month. Sign up for the free trial and as long as you cancel before the 14 days are up you won't be charged. Of course I have over 750 videos right here on TH-cam as well, but all of my classroom lectures that I recorded over the years with my class are on my website. www.scannerdanner.com Thank you! Hope to see you there.
Is it common for cars such as a ford f150 and ford SUV to use the same voltages to set up a fault or typical run conditions such that you could take one from one of these cars and adapt it with fittings to the other and have the system work? :-) My 04 F150 has a inline sensor and is difficult to find( and is expensive as they want to sell you all the fuel lines with it), and the other Fords have a in tank plug in unit that you can find anywhere for cheap! Thanks for your time and expert information.
No you cannot. If the sensor is unplugged and you read 0 volts on the signal wire, it is NOT a ground, it is still the signal wire, there just isn't any voltage on it with the sensor unplugged.
Would a Fuel tank pressure reading of -33 mmHg with the fuel tank lid off indicate something is plugged and pulled vacuum, if the sensor tests well? Threw a code for evap vent, tried to actuate it manually with scan tool and a message popped up on my tool that the vacuum is too high and stopped it from opening. Haven't really looked at much yet I suspect something is plugged or stuck. Buddy's truck, just doing preliminary research.
AT 16.47 in your video, you are jumping Signal to Ground. When you jump Signal to Ground, it is like kind of short(basically connecting + and -) there will be a current flow. If you look at 16.47, Singal REF wire have >>>> 100 kilo ohm resistor connected in series with Signal wire and you are jumpting that signal wire to ground. In a series circuit current is same across every point. I assume 12V/100000 gives .00012 amp(ohms law), very very less, so that is why it is ok to jump Signal to Grd ?
I’ve tested my FTPS using a vacuum pump and back probing the sensor connector with no vacuum on the sensor I was reading around 1V but once I applied say 10”hg I then was reading around 4.5V. So my question is what should voltages be for any given amount of vacuum?
Hoping you'll see this ScannerDanner. I been fighting an P0455 code on my 06 Silverado now for quit some time. I have 'verified' no leaks in the system. Using an SnapOn scan tool the (new) tank vent valve NEVER closes, but, can be closed manually with the scan tool, and I've verified i does seal off. Also the purge valve continually stays open and never closes. It's like the tank sensor is giving the PCM false readings, or there is something wrong with the PCM. The PCM had been changed after my local dealership said it was giving some strange readings. It was replaced with a used (reflashed for my vehicle) PCM. I've tested the tank sensor wiring like you showed here and I get the 5v reading on the scan tool, so I know at least those two wires are good, but, could a bad ground from the PCM be causing my problem. The sensor voltage NEVER changes from a constant steady reading sitting at an idle, or driving on the highway even after trying 2 different tank sensors. one sensor stayed at 1.2 volts, and the other stays at 1.5 volts on the scan tool. 'COULD' it be the blk ground wire back to the computer causing this, or something else? This thing is about to drive me NUTS!!!!! LOL! WHAT could be causing both valves to stay open ALL the time?
I wouldn't be worried about the tank psi readings if your purge valve is always open. You have multiple problems, lets start with the purge solenoid. What are your voltage readings on both wires on the purge solenoid with the KOEO? KOER @ idle?
OK, hoping I'm covering what you're asking for. KOEO purge valve 'unplugged 12.13 volts, plugged in 0.00 volts. KOER purge valve unplugged 14.23 volts, plugged in 0.00 volts. After 'closed loop'? purge valve plugged in 1.09 to 1.21 volts varying. What say you? Thanks for your help. :)
Paul, I love your videos. I also follow Daniel Sullivan's videos and he is a big fan of "ghost" voltage and specifically how it tells you something important - namely that a circuit is open. Short to ground would be 0V, ghost voltage is open. Do your meters not show ghost voltage or is there another reason you don't mention it?
if we didn't have a wiring diagram we could use the test light connected to the battery positive to find the ground? in the ground it would light up while in the signal it wouldn't light up?
Sorry, I forget this point, Let say we have A B and C as three points. A is Signal Reference connected to B via a resistor of 100 Kohms in series then you are jumping B in series with C (ground). As I explained between A and B current is .00012 amp(12v/100kohms), then current between B and C will be huge(right, bcz u have sorted). So the current at point A is equal to .00012+ current (between B and c). Since current is same at all point A, B and C, will not we fry PCM?. Again I may be stupid ?.
If the open circuit on the signal/ground wire was after the voltage sensing circuit wouldn't the voltage SC read 0 volts? As it would no longer have a ground connection to read the 5 volts comming from the signal wire or "resister" or whatever thats called. So a short after the sensing unit would cause a zero volt reading, is that correct?
Resistance testing is an option, but the ECM and sensor need to be unplugged for proper readings. This test eliminates the need to unplug the ECM, so major time saving step.
ON THAT TRUCK DID YOU REPLACED THE FUEL PUMP? OR JUST THE FUEL PRESSURE SENSOR. I AM WORKING ON A 2000 S10 2.2L AND I DID REPLACED JUST THE SENSOR BUT I STILL HAVE THE CODE.THE SIGNAL ,GROUND,AND 5V REF ARE OK.I HAVE P 0452 AND P0462 WICH IS FUEL LEVEL SENSOR LOW..THANKS
I'd just call them variable resistors and get away from people getting caught up on the potentiometer confusion. The potentiometer is a variable resistor as well..
Hey Paul, happy new year. Ive got a question on the design with the resistor being connected internally on the signal line. You say unplug the connector and you should see 5 5 and 0, and that if you see that, then you can replace the sensor as the signal cant have an open or short. What if however the signal wire was corroded and you unplugged the connector? Would you still not be reading 5 5 and 0 due to there being no current flow on the signal? I would assume this is where jumping the ref to the signal would come in to play as if there were green cruddies on that signal wire then we would have a voltage drop at the computer? Thanks alot
Paul. If we had the second design (one with internal resistor) as stated at 15:00 to 15:30, and there was a short to ground in the signal wire between the connector & pcm. Then we unplugged the connector, then the scan tool would read 0 volts as in the top design and not 5 as you stated. Would that be correct?
Sorry for the previous post. What I was going to mentioned just for reference is that most GM vehicles have a 1.47-1.50v reading on the tank pressure sensor with no vacumm or pressure in system. Thanks
Should the resistance values for the FTPS be the same as the MAP sensor? While testing the MAP sensor with vacuum pump and multimeter, the more vacuum I put on the sensor the more voltage I would read, but on the FTPS tested the same way, as soon as I’d get virtually any vacuum on it it would go straight to full voltage.....is this normal?
For an average home owner that does not own an advance scan tool, can I use a volt meter link in series with a test light and use the reference 5v to test the ground and signal wire. I know that I can do a continuity test to verify ground also but what about the signal wire? Will that damage the computer module?
Step 1: with the key on engine off, measure all 3 wires with your voltmeter. You don't need a test light for psi sensor testing, nor do you need to do continuity tests. Tell me what you have on all 3 wires with voltmeter negative lead connected to a known good ground
+littlebear gaming Thanks again for your support. Unfortunately I cannot keep up with the number of technical questions I get from my subscribers through email anymore but I have created a forum for you guys for this very thing! www.scannerdanner.com/forum.html Thanks for understanding.
Quick question: So I don't have to check for pressure in the system? My car car 2011 Nissan altima s 2.5. And I was planning on doing a pressure test first. I think I'm missing some information. Or I'm not understanding the code. You didn't suggest it, so now don't know if it's necessary. Code: p0452 sensor/switch low. Thank you very much for your videos.
I need to check service info, but this sounds like a tank psi sensor code. And with a circuit low code, you'll be focused on the sensor and wiring and not worrying about what the tank psi actually is.
I was thinking on pressure testing the system first,cause my car after sitting overnight smells like fuel vapor. Both valves are good and their wiring is good too, including the sensor wiring. I'm left with the sensor itself. or with an evap system leak . Can the p0452 sensor/switch low code also mean .low enough Pressure? Or is that code primarily to the Pressure sensor? Thanks again.
Focus on the psi sensor first for that code. I know you smell fuel, which does suggest a leak too, but that system will not be able to run the leak test with a faulty tank psi sensor. So you may have two problems
The guy who ran the code reader test , also put my new fuel-pump in , He said the Evap was good , but the code still said PO446 on my 2000 chevy Blazer.. Was he B.S. me.. Is the canister purge valve & vent valve solenoid the same part ?
+Doreen Gotti they are different parts. the vent solenoid is normally open valve that closes when the engine computer tests for leaks and also closes when the purge solenoid is commanded on by the engine computer
If your ground is also reading near 5v, then yes, you have a bad sensor ground. These are usually shared with other sensors before grounding through the computer board. Check some of the other sensors and see if they have bad grounds as well, this will dictate your next move. A bad ECM main ground could also cause this issue.
What's missing which is very important is where the scanner is plugged in when ref is jumped to signal.....it has to be connected to the PCM?? But where and how?
Good video i have same troble code but only happen when summer is here, i check wires remplace connector, ecm and the sensor still having the low signal from fuel thank pressure sensor, i saw on google the a/c pressure switch it may be affecting. What other possibility can be it??
I am directing all help requests to my forum. Sign up (it's free) and create a new post. Be sure to add a name under "alias" as this is the name that will appear in the post. Here is the link to the forum. www.scannerdanner.com/ForumRetrieve.aspx?ForumID=3226 Thanks
might be a dum question , when you have a 5-0-0 sensor disconected and "no wiring diagram" how do recognize wich of the to 0volt wires is what . (one of the two will have continuity to ground?)
I have a 2008 f150 4.2 L and I'm getting a code of P0453. I did some checks and saw my pressure sensor value was NOT moving, so I decided to change it out. After changing it out, I'm getting a stuck negative pressure. After looking at this video, I attempted to test the sensor, but I'm stuck at determining which are the two wires to jump. I don't know which one is the return signal wire in order to jump it with the 5 volts reference because I'm getting low voltage (millivolts) in the remaining both wires. When I unplug the sensor, I'm getting ~6000 pa. And, when i plug it back in, I'm getting -1760 pa. Could you help me to identify which of the other two wires have to be jumped and to check the integrity of the wiring circuit? Thank you very much.
@@ScannerDanner I used a test light on it already to try to determine which one is the ground using a direct positive wire from the battery and found only one wire is completing the circuit. Is that wire a direct ground or a controlled ground from the ECU? Secondly, why would I get a NEGATIVE reading on my scanner live data when I attach the connector to the sensor and a MAX reading when I disconnect it?
Hi ! a question : I have an Opel (group gm) i suspect an evap solenoid valve fault, only i do not have a fault code displayed on the dashboard. Is it possible to find faults with a pro diagnostic device, which would not be indicated on the dashboard of the car? thank you ! ( Thomas, from France )
Great video! I had the same concerns as others about jumping VREF to signal, just in case the signal wire has a short to ground. Would testing continuity from signal wire to ground be a good enough pre-check? Also would it not be safer to suggest building a 5v power supply tool to keep in your box instead of ever jumping a VREF? Or why not just use a 12v power probe?
Watch my video called Signal Circuit Integrity Update for my Ebook Also to put your mind at ease with this, the 5v regulator is internally protected by the PCM. You will not fry the reg. if it is shorted to ground. I wouldn't recommend doing so but if you did, once you fix the short it will come back to life. Here are two videos with shorted ref. circuits that came back to life once the short was fixed. 2006 Cadillac DTS Shorted 5v Reference Circuit 2005 Honda Element No Start, No Communication (case study)
I did watch that video, and it is an important update! But wouldn't it be kind of safer and easier to build a tool for supplying 5v without using the pcm's VREF circuit? Think 5v Power Probe. Also what would be wrong with using a 12v power probe for circuit integrity testing? Won't it just show up as 5v on the scantool?
Steve Hulett You could do that too and I have used a 12v test light for this type of testing and it works too although I would recommend an LED type just to reduce the potential for too much current. And of course the 5v power probe would be ideal for this. I have read, that feature is available with the power probe hook?
ScannerDanner You're right about the Power Probe hook! Sweet product. It lets you supply between 0 and 5 volts in 1/2 volt increments. That's pretty handy since it lets you adjust it to a level low enough to not even trigger a fault code for out of range! It also lets you send continuous or pulsed voltage. Well, here... www.powerprobe.com/hook.php
I did the same test on a oil pressure switch while looking at data jump the wires I got my 5 volt but my pressure reading stay the same any advice will be helpful
Hello Sensei. I know this is VERY long in the tooth, but it remains such an excellent reference -- I'm HOPING.... (that you'll see this - and can drop a HINT???) I've an 05 MB E320 that's failing smog cert because of a recurring P0453 - FTPS signal TOO HIGH. Neither of my scanners (iCarSoft MB II and BlueDriver) will allow me to monitor that signal, so I tapped into that wire so I could monitor the voltage with a DVM. Initially I was seeing about 2.5v, then later (as the day got hotter?) I saw about 1.5v. Fine, I thought - so WHERE is this TOO HIGH thing coming from? Well, here's the reason I'm halting my own edumacation via your videos to ASK: This signal line has been showing me (virtually) ZERO volt diff to the ground line (0.001, actually). so I am BAFFLED! Should I be baffled, or should I know that this actually MEANS SOMETHING? FWIW - I do not have what you refer to as a 5-0-0 circuit: mine reads 5-4.97-0 - so I conclude it has the internal resistor. I never know what to expect (for the voltage level on that signal line) - it sometimes shows me that (reasonable) 2.5v reading - until I look away and then look back. It's MESSING with the vacuum level in my skull!
Great info so far! The 4.97 is your signal. I would monitor that signal wire at the ECM connector while your driving it. That high voltage code is suggesting an intermittent open in the signal wire or the sensor ground. Or a faulty sensor. But you're going to see that signal voltage rise to that bias level as the open is occurring. You may not see the full 4.97 either, but it's going to seriously mess with those voltage levels and in the opposite way when measuring at the sensor, that is if our open is on the signal wire. If our open is on the sensor ground, it will measure no different at the PCM and Sensor. Lol I'm rambling
@@ScannerDanner I am humbled and honored that you bless me with your time to answer - and so promptly, to boot! As it happens, I did find that I CAN read the voltage at the PCM (with my iCarSoft MB II) so I believe I CAN complete the homework assignment. It occurs to me, however, that I might need to confirm the best place to connect the ground lead of my DVM: as it stands it's on the ground wire of the sensor wiring; but I wonder if I shouldn't oughta move it to a chassis ground instead? Or perhaps connect another DVM with its positive lead on the ground wire of the sensor wires and its ground lead to chassis? Anyway, in advance of this next test session (while I'm driving to return the sensor I bought - which doesn't fit) I might offer this near-useless tidbit: I was already leaning toward suspecting the sensor failing - and your comment tends to confirm my weak intuition that way. But - according to an obscure corollary of Murphy's Law - the thing will behave just fine - as long as I am LOOKING at it. But as soon as I look away..... I mean - what are the odds that I'll happen to be looking at it WHEN it exhibits its little quirk? I'll give it a go, though. Thanks again!!!
@@YahWho-is1tt yes, battery ground when possible. Sensor ground is okay, only when you want to clean up a noisy signal on a scope. Other than that I never use sensor ground when troubleshooting something like this, because sensor ground could be one of the problem areas! It should read .1v or less on that sensor ground when compared to battery ground, with the circuit loaded (Key on or engine running)
@@ScannerDanner Well, yesterday's driving experiment has thoroughly confused me! I drove about 75 miles in three major stages (IOW made 2 stops of about 2 hrs each). Watched voltage at ECM/PCM with scanner and on signal wire at sensor with DVM. NEVER did I see any significant discrepancy (aside from tiny fractions and slight reactionary time differences. At start of drive the voltage was about 4.85, but it immediately started dropping slowly - was down to about 3.6 by stop #1, and about 2 after stop #2 - which was heading home. Down it continued, until it was down to 0.02v (which corresponded to -60 mbar). I thought perhaps the consumption of fuel was creating more of a vacuum inside the tank, so I stopped and opened the gas cap, but when I did I heard/felt NO sign of vacuum as the seal broke. Nor did that make ANY difference in the voltage reading. What DID happen at that point, though, was the CEL came on with a DTC of P2012-000, NOT the P201C-000 that has been plaguing me (causing the smog cert failure). So I'm getting codes pointing at both the tank pressure sensor AND the charcoal filter valve/solenoid. The latter I have not yet examined - but I was told to check the wires for rodent damage. I also read that the EVAP system test does not run until a full tank has been run down to about 3/4, which is ball-park close to where the voltage dropped to nil - but that is merely a long-shot guess on my part at this point. Does that slow, steady drop make any sense to you, by any chance? I have a new sensor, but its electrical connection does not match that of my ?OEM? one, so I am waiting for the necessary adapter - at which time I can (hopefully) replace the suspect sensor (with a tricky surgery - as more than the elec jack is different!) Wheeeeeeee - such FUN! (as your tab continues to grow....)
AN IN THE 5-0-0 SYSTEM INSTEAD OF A JUMB WIRE WE PUT THE TEST LIGHT TO BATTERY POSITIVE AND LOOKED AT THE DATA WE WOULD NOT SEE THE INTEGRITY OF THE WIRE? THE SIGNAL WOULD NOT GO UP? WE DON'T HAVE A PULL UP SYSTEM?
@@ScannerDanner BECAUSE THE TRANSLATION IS WRONG TELL ME WHICH IS CORRECT 1)JUMB SIGNAL AND REFERENCE WITH TEST LIGHT? 2) CONNECT THE BATTERY POSITIVE TO THE TEST LIGHT AND DO WE TOUCH THE SIGNAL?
@@ScannerDannerThanks for responding.. The snapon scanner says Evap system incorrect/no purge flow. I'm stumped on this and i don't have a garage. So trying to diagnose this outside sucks. Its really cold up here in ny lol.. maybe you can pin point me in the right direction. I'm working on my friends 2005 kia sportage 2.7L auto 4x4 with 90k miles. Im trying to pass inspection but i can't seem to figure this out. I replaced both the purge and vent valve and the same code keep comming up. Also idk if this might help but my friend told me when he fills it up, it becomes a crank no start, so he never fills it up all the way and its fine as long as he does that. I checked the FTP sensor on the scanner and its reading zero hg. Im not familiar with the evap system so much or what kind of readings the FTP sensor should be. Can it be a faulty FTP sensor or clogged charcoal canister? Thanks, Pablo
@@pablomarquez4431 I just did a Hyundai (same exact electrical system) with an aftermarket purge valve causing large leak codes. I wouldn't be surprised if your issue is being caused by an aftermarket purge valve. It MUST be a bosch purge valve (bosch is who makes the valve for the factory on these) Here is the link to the final part of that series th-cam.com/video/ipTSsmZhZxo/w-d-xo.html
I know this is an old video, but have you ever seen a P0451 on a Ford Pickup? mine is a 04 5.4l F150 Lariat. I have looked at the sensor and grounded the signal and the voltage went to 0 and took the 5v to signal and got 5v. The voltage changes but I guess not enough. Suggestions on how to proceed?
Hi there sir I've got a 2011 silverado it's throwing a p0449 code I changed the evap vent solenoid and it still comes back on the vent solenoid is clicking when the vent solenoid is hook to the charcoal canister I can't put fuel in it but I can when I disconnect the line from the canister will a bad tank pressure sensor cause that
@@shannoncarroll3600 okay, it absolutely shouldn't be doing that and that is why you can't fill your tank. Your control wire is shorted to ground or the ECM driver for that vent solenoid is shorted. Do a really good visual on that harness!
Great question! You would be shorting the 5v ref circuit to ground. What would happen as a result? You'd lose scan data as the ECM would stop communicating (on a single 5v reg system) As soon as you take your jumper off and cycle the key the 5v would come back. I've modified this test in later videos and suggest using an incandescent test light as your jumper wire so as to act as a buffer if the signal wire is shorted to ground.
@ScannerDanner Yes, in addition, I looked at the internal structure of the power supply system, which is an integrated circuit (buck converted ). Able to deal with situations such as short circuits. Thank you so much, Mr Paul
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Wow! I wasn't expecting anything like this video turned out to be. I feel like I just subscribed to a class and I'm about to be a certified home technician. Good stuff! Very impressed with your work and when you through it on the white board, I was blown away! Keep up the great content! Thank you for your time
I think people should buy Mr Paul's book as a appreciation for offering invaluable free knowledge and also to encourage him to make more videos.
it sounds like someone is snoring in the background!
Pay Attention kid your getting taught by one of the best!!
OUTSTANDING!!!
I personally appreciated the professional approach and clear explanation of the electrical issues a automobile might have.
Great learnig.experience.
THANK YOU.
Hello
Just wanted to say that i am blessed to see any of your videos!!
You made a huge impact on me and gave me knowledge that most people will not do!!!!
Thank you so much sir!!!!
You are so welcome! Thank you!
That is a great question! One way is to look at some of the other sensors wire colors. Grounds are typically shared between sensors. Also if I see a 5-0-0 sensor I will jump the ref. to the signal using a 5kohm resistor and watch scan data signal for 5 volts. If you use the resistor and jump the ground by mistake = no harm, no foul. DO NOT do this without a resistor if you don't know which is which
Thank you very much. It is hard to ignore the negatives. I just need to remember that I don't need to always defend myself. I have always let me work speak for me. It was really cool of you to defend me over there. I truly am grateful.
As an instructor your a natural communicator. The information you provide is priceless. I do wonder if your students absorb the info considering all the variables to every circuit design by manufacturer. I wonder if its possible to be a general service technician at all or do we train techs to specialize entirely on the electrical diagnostic side of the business only and some on the mechanical side of the business.
Thank you! Great video it helped solve my issue with emission monitors not being ready. The aftermarket fuel pump had the 5V Ref and PCM signals swapped at pigtail. After I swapped the pins on 8 pin connector I got 2.7 V where before I was getting 4.07. I wonder how many fuel pumps were delivered with that quality issue. Thanks to this video I was able to get 2002 Mustang to pass CA smog.👍🏽👍🏽
Awesome! Thank you
didn't have chalk boards like that in my school. great vid
KNOWLEDGEABLE Sir ScannerDanner
Thank you 👍 Take care
Sir ScannerDanner
From Nick Ayivor from London England UK 🇬🇧
I was also wondering about the question below (everxxxx), about possibly jumping the 5v ref to a shorted signal wire and causing damage.
Would also like to recommend Paul's book, explains things well and if you're still not sure about something he always responds to emails to your questions. Top guy!
@Bonfield2002 Thank you very much for the compliment. I always tell my students that it will take years to absorb all of the info I pound into them with my class. This is why I created this "field manual" (my book) for them to take with them in the field. It is the one book they will want to keep in their toolbox!
The previous post, I accidentally wrote batterias. I hit send before I was completed with my response. Sorry about that. By the way great videos with a lot of very useful information. Thanks
Thank you very much for this very detailed video! It helped me understand why I have voltage on the signal leg of my VPS with sensor unplugged.
That's what I'm talking about! When you start to understand bias voltage and how to use it, it will change how you troubleshoot opens and shorts in wiring harnesses.
This is a great Video, I will be happy to have an instructor like you you all day long.
Thank you Sir.
You are correct my friend. This is why I did another video. I called it "Signal Circuit Integrity Testing Update for my eBook"
Also Section 10 in my eBook "Signal Circuit Integrity Testing" I have addressed this issue.
Thanks!
Hi Paul
I am fairly new to troubleshooting cars.I just watched the video that you and Eric did on misfire.It was awesome as usual. Some of the comments are proof that how many people do not appreciate your level of skills and understanding of Automotive electronic and computer diagnostic.I mean try to explain what an ATTENUATOR is to Joe the muffler man .Please ignore the negatives an focus on positives which are way more as I read.
Keep on the fabulous job that you are doing.Thank you
NOT ONE TAKES ABOUT, Other Reasons Why You Get Po452 code. I have a 2004 Silverado that sat for along time. I removed the fuel pump assembly, empty the tank, wipe clean and reinstalled all. Tried to start engine, it would crank, but hot start. Sprayed starter fuel into intake and it would start then die when starter fuel ran out. When to Auto Zone and paid $140 (Refundable if returned in 90 days) and found I had a P0452 code. I kept thinking it had to do with the opening of the fuel tank. Finely (After watching hours of videos) decided to remove fuel pump system. Cleaned opening and o-ring making sure o-ring was in the slot. After installing fuel system, noticed o-ring had come out, moved back into the groove, installed ring, and all connectors. After cranking 2 times, fired right up. All side remember hearing that if the gas cap was not tight or was leaking can cause the same problem. I wanted to pass along since I did not find a single video taking about the solution of a lose of pressure or a failed gas cap under P0452 code.
William R Martin
Thank you very much for this video, man. I have difficulties understanding lessons but you made it very clear for me to understand, a little quick here and there but great work non the less! My 2001 Z28 Camaro has a P0452 Engine light and I will test it tomorrow to confirm it's a sensor, thank you very much once again for the video!
All I can say is, "Thank You" Oh, one more thing... Genius!!!
This is great, I've been fighting a P0451 & intermittent P0452 codes on my Escape. I'm going to do this test tonight to confirm my sensor is good or not. I'm a subscriber after this video!
Adam S Hi buddy you can fixed your cod.. I have the same problem same code..
Parabéns meu amigo, sua explicação é impressionante!
There will be current flow but it is even lower than you stated as it is a 5v source not 12. In fact the sensor itself pulls this "bias" voltage to almost ground at times. So there is absolutely no danger in doing this test. Also the internal resistor may be even higher ohms than I stated.
Very informative video. thank you
Hi and I’d like to thank you for this video, awesome explanation keep doing your great job great for you!!!!
This is a great video, but you said never short the 5v reference to ground or computer damage can happen. but if the you are jumping the 5v to signal to see cicuit integrity of signal wire, and lets say the signal wire was shorted to ground seems like that can cause internal damage to computer. The reason I asked because 0v in the scan tool can be caused by a short or open in signall wire. not trying to judge the video maybe something I am missing.
I have your E-Book and its great.
Just simply amazing. Great job.
No! You wouldn't want to put direct 12v into the O2 signal wire. There is some protection inside the PCM for the O2 signal circuit. I just wouldn't jump direct 12v to it. Use your body as the resistor and do it that way.
@ScannerDanner leave the PCM plugged in, make sure your ohmmeter is reading in the kilo ohms or that it's just not reading zero. And no the ohmmeter will not hurt the PCM on this test.
You are amazing and great teacher
Great explanation. Thank you.
Great explaination and easy to understand 👍❤ , btw i think someone was sleeping during that class ! I hear a weird sound in a background lol 🤣
Yeah, it was a student in the back of the class smh
Respect! And knowledge! Thanks✌️
The kid snoring in class will be the tech at the Chrysler stealership who replaces a gas cap 3 times for an evap leak, when it really there was a cigarette-sized hole in the purge line caused by rubbing against the ECU harness (COUGH THIS HAPPENED TO MY CUSTOMER). The passionate tech's will prevail.
@ronlyon77 Thanks for the comment about the book! Read below about the ohm test question and it is a valid point.
I done this same test on a car at work the other day, but it had a FTP sensor performance code. If you touched the top of the sensor the voltage pid on the tech 2 would go nuts.
@jtech23 LOL you caught that! This poor kid has sleep apnea and he was sitting right next to the camera. Did you see my face when that happened. It was kind of funny. He is really trying, I don't fault him.
@EVERXXXX You could certainly do that, however in my experience a shorted reference circuit almost always comes back to life after fixing the short so I'm not to concerned about it.
I have watched this three times and I got it the first time. Great information but most techs can't do that. I have one question though: Why not just replace the sensor? I do have a scan tool but I guess the stealership does not. They replaced the fuel pump under warranty and a couple of days later the car will not start.
I have an Innova 3040c and P0452 is what it told. The stealership told me that I needed new spark plugs that cost $505. I went down to the stealership and observed the plugs.(not an old car). The plugs were fine. Not my first car.
I priced out the part and it is $33 plus tax. Look where it is located though. I appreciate what you are putting out there for facts. There can be so many other things wrong with an EVAP low fail. I have 0 degrees F here with a twenty mile an hour west wind. I know what I can do but that is why I have four vehicles. You would think that the stealership would take some ownership on their warranties.
I hate to be at 75% operational. It is Minnesota though and I only have one non-heated garage for cars/trucks. You have to get the vehicle in the garage first though.
@ScannerDanner If you check the signal wire for a short to ground you would have to unplug the PCM for a proper test and we want to avoid that step if possible. I suppose you could.....
Very helpful. Thanks!
thank you!
Thank you.!!
You are very welcome my friend.
Hello Mr Danner Thanks for this information
My question is about jumping 5 v reference to signal wire. What if the signal wire was shorted to ground but you jumped 5 v reference to signal wire. Is that same as jumping 5 volt reference wire to signal wire to ground wire in the bottom
you mention here dont jum 5v ref to ground,that means with jumper wire or testlight,but if i want to check 5v ref voltage with multimeter,i can do that? one lead to 5v ref ,other to ground,scale on 20v DC. its dwont hurt that regulator?
good job teacher ScannerDanner :D
2006 Chevy Optra (p0454, then p0452) - this is the same car as Suzuki Forenza/Reno(USA)
Hello Paul,
I have followed your Video instructions and below are the tests i have performed on the FTPS problem so far. I am a DIY'er and seem to have hit a block in the road.
I have no wiring diagram for this cars FTPS circuit as i cannot find
one. I have a service manual for a 2004 Optra and it doesn't list
anything for the FTPS circuit or ECM pin layouts
NOTE: I do not have a Fancy dancy scanner with square waves etc. I only have a simple Actron scanner CP9580a and a DMM and test light.
Here is what i have diagnosed so far:
(( CONNECTOR UNPLUGGED ))
With Key off
-------------------
1.) I have continutity on the ground wire(black)
With Key on Engine off
----------------------------------
2.) 5Volt Reference - tested 4.99V on the reference wire (gray)
3.) Signal Wire - jumped 5Vref to signal and backprobed the signal wire
(ecm side of connector). Test showed 4.99v proving no connector fault.
(( CONNECTOR PLUGGED BACK IN ))
4.) FTPS test - removed FTPS from Fuel Tank Pump assembly and applied
-10kpa vacuum on the sensor and it ranged from 1.3v - 4.74v
After releasing the vacuum pressure voltage returns to 1.3v ,,,,Did test 2 or 3 times to verify.
5.) Purge Valve - removed from car and applied voltage to test valve open close operation while applying vacuum - Valve opens. Also listened to the purge duty cycle with stethascope and valve was rattling away.
6.) Vent valve - removed from car and applied voltage to test valve
open close operation while blowing thru it - Valve closes.
7.) Gas cap is brand new.
8.) The Drive Test Diagnosis - The MIL IS ON !!!......
After resetting MIL and now 93km later the "Evap Drive Cycle Monitor" is
complete and "DTC P0454 is confirmed". P0452 hasn't reappeared as yet,
but rest assured it will as i have done this a few times already over
past year.
With the DMM connected to ground and backprobed to the signal wire on
connector (ecm side) i observed the Voltage reading while driving for 15
minutes. At very low load The signal was perfect (1.4V-3.1V).
Went home let car cool and retested. Drove same distance never tromping
on throttle. Stopped, waited a few minutes and restarted car and the MIL
went off (expected). All the drive time the FTPS signal Voltage was
perfect and MIL went off.
SO I APPLIED SOME FORCE TO HER ON THE NEXT TRIP FLOORING THE GAS PEDAL
WHILE OBSERVING THE DMM VOLTAGE and sure enough the voltage dropped
below threshhold and went haywire at times. This resulted in the MIL
coming back on IMMEDIATELY after the second attempt. I am almost sure
that the code is being set when there is positive pressure in tank,
because freeze frame data indicates PURGE % = 0.
Below .1 Volts i think is the threshhold which has to happen on 2
consecutive trips for the MIL to come back on and my testing confirmed
that.
But i have reservations about going out and replacing the sensor
(throwing money at parts) until am absolutely sure about the fix.
9.) Commanded the Vent valve closed with my scanner and applied .5 psi shop
air from the evap hose before the purge valve. Everthing seemed to hold
pressure but i have no way of determining this as I dont have a fancy
smoke machine with pressure gage). So i attached a balloon to the Vent
Solenoid end of EVAP system and waited 10 minutes. Came back and the
balloon was still holding all pressure, so it seems that i have no
leaks, thus no leak codes....dah!!
PAUL PLEASE ADVISE, AS I AM NOT SURE WHICH FORK IN THE ROAD TO TAKE FOR THE
NEXT STEP. I dont have a wiring diagram showing the FTPS circuit nor do
i have a pin layout of the ECM to do a short / open testing on the REF
& signal wires. You mentioned in your video not to worry about ground wire in this case and it makes sense.
If anyone has the FTPS wiring diagram and ECM pin layout i would be forever grateful as i cannot find them anywhere on the WWW.
Whats really puzzling is that I have a 2004 Optra Service Manual but it doesn't show any information regarding the FTPS.
PS> I LOVE YOUR VIDEOS - YOU ARE THE BEST TEACHER OUT THERE BAR NONE !!! .....well maybe the legend scotty K.
So, in the top example at frame 16:46, you say that jumping the 5v reference to ground will fry the pcm regulator. If i'm following what you are saying, why would they make an expensive pcm so vulnerable to a short to ground?
It won't kill it. It will pull it down until the short is fixed, then it will return
scannerdanner rocks,cool
I am trying to learn about vehicles and your instructions are very easy to understand. As someone that is now beginning where should I start. How do I get a hold of the circuit
Start with my classes I offer on my website! I have over 400 hrs of training material available for $11 a month. Sign up for the free trial and as long as you cancel before the 14 days are up you won't be charged. Of course I have over 750 videos right here on TH-cam as well, but all of my classroom lectures that I recorded over the years with my class are on my website. www.scannerdanner.com
Thank you! Hope to see you there.
thank you for the tip. oh and what previous comment?
Is it common for cars such as a ford f150 and ford SUV to use the same voltages to set up a fault or typical run conditions such that you could take one from one of these cars and adapt it with fittings to the other and have the system work? :-) My 04 F150 has a inline sensor and is difficult to find( and is expensive as they want to sell you all the fuel lines with it), and the other Fords have a in tank plug in unit that you can find anywhere for cheap! Thanks for your time and expert information.
No you cannot. If the sensor is unplugged and you read 0 volts on the signal wire, it is NOT a ground, it is still the signal wire, there just isn't any voltage on it with the sensor unplugged.
Would a Fuel tank pressure reading of -33 mmHg with the fuel tank lid off indicate something is plugged and pulled vacuum, if the sensor tests well?
Threw a code for evap vent, tried to actuate it manually with scan tool and a message popped up on my tool that the vacuum is too high and stopped it from opening.
Haven't really looked at much yet I suspect something is plugged or stuck.
Buddy's truck, just doing preliminary research.
AT 16.47 in your video, you are jumping Signal to Ground. When you jump Signal to Ground, it is like kind of short(basically connecting + and -) there will be a current flow. If you look at 16.47, Singal REF wire have >>>> 100 kilo ohm resistor connected in series with Signal wire and you are jumpting that signal wire to ground. In a series circuit current is same across every point. I assume 12V/100000 gives .00012 amp(ohms law), very very less, so that is why it is ok to jump Signal to Grd ?
thanks
I’ve tested my FTPS using a vacuum pump and back probing the sensor connector with no vacuum on the sensor I was reading around 1V but once I applied say 10”hg I then was reading around 4.5V. So my question is what should voltages be for any given amount of vacuum?
Hoping you'll see this ScannerDanner. I been fighting an P0455 code on my 06 Silverado now for quit some time. I have 'verified' no leaks in the system. Using an SnapOn scan tool the (new) tank vent valve NEVER closes, but, can be closed manually with the scan tool, and I've verified i does seal off. Also the purge valve continually stays open and never closes. It's like the tank sensor is giving the PCM false readings, or there is something wrong with the PCM. The PCM had been changed after my local dealership said it was giving some strange readings. It was replaced with a used (reflashed for my vehicle) PCM. I've tested the tank sensor wiring like you showed here and I get the 5v reading on the scan tool, so I know at least those two wires are good, but, could a bad ground from the PCM be causing my problem. The sensor voltage NEVER changes from a constant steady reading sitting at an idle, or driving on the highway even after trying 2 different tank sensors. one sensor stayed at 1.2 volts, and the other stays at 1.5 volts on the scan tool. 'COULD' it be the blk ground wire back to the computer causing this, or something else? This thing is about to drive me NUTS!!!!! LOL! WHAT could be causing both valves to stay open ALL the time?
I wouldn't be worried about the tank psi readings if your purge valve is always open. You have multiple problems, lets start with the purge solenoid.
What are your voltage readings on both wires on the purge solenoid with the KOEO? KOER @ idle?
I'm away from the truck for the weekend. I'll have to get back with this probably on monday. Thanks fir the reply, it's been kicking my butt! LOL
OK, hoping I'm covering what you're asking for. KOEO purge valve 'unplugged 12.13 volts, plugged in 0.00 volts. KOER purge valve unplugged 14.23 volts, plugged in 0.00 volts. After 'closed loop'? purge valve plugged in 1.09 to 1.21 volts varying. What say you? Thanks for your help. :)
Paul, I love your videos. I also follow Daniel Sullivan's videos and he is a big fan of "ghost" voltage and specifically how it tells you something important - namely that a circuit is open. Short to ground would be 0V, ghost voltage is open. Do your meters not show ghost voltage or is there another reason you don't mention it?
@Username64870 Nice! I agree completely of course :)
if we didn't have a wiring diagram we could use the test light connected to the battery positive to find the ground? in the ground it would light up while in the signal it wouldn't light up?
That is correct, but an LED type light could be misleading
Sorry, I forget this point, Let say we have A B and C as three points. A is Signal Reference connected to B via a resistor of 100 Kohms in series then you are jumping B in series with C (ground). As I explained between A and B current is .00012 amp(12v/100kohms), then current between B and C will be huge(right, bcz u have sorted). So the current at point A is equal to .00012+ current (between B and c). Since current is same at all point A, B and C, will not we fry PCM?. Again I may be stupid ?.
If the open circuit on the signal/ground wire was after the voltage sensing circuit wouldn't the voltage SC read 0 volts? As it would no longer have a ground connection to read the 5 volts comming from the signal wire or "resister" or whatever thats called. So a short after the sensing unit would cause a zero volt reading, is that correct?
Thank you this was very help full but is it possible to check this by check resistance between the 5v wire and the signal wire?
Resistance testing is an option, but the ECM and sensor need to be unplugged for proper readings. This test eliminates the need to unplug the ECM, so major time saving step.
I think you have to use a 5000 resistor instead wire in case you have short to ground in signal wire just for safety for the 5 reference circuit
A test light works as a buffer as well
ON THAT TRUCK DID YOU REPLACED THE FUEL PUMP? OR JUST THE FUEL PRESSURE SENSOR. I AM WORKING ON A 2000 S10 2.2L AND I DID REPLACED JUST THE SENSOR BUT I STILL HAVE THE CODE.THE SIGNAL ,GROUND,AND 5V REF ARE OK.I HAVE P 0452 AND P0462 WICH IS FUEL LEVEL SENSOR LOW..THANKS
I'd just call them variable resistors and get away from people getting caught up on the potentiometer confusion. The potentiometer is a variable resistor as well..
Hey Paul, happy new year. Ive got a question on the design with the resistor being connected internally on the signal line. You say unplug the connector and you should see 5 5 and 0, and that if you see that, then you can replace the sensor as the signal cant have an open or short. What if however the signal wire was corroded and you unplugged the connector? Would you still not be reading 5 5 and 0 due to there being no current flow on the signal? I would assume this is where jumping the ref to the signal would come in to play as if there were green cruddies on that signal wire then we would have a voltage drop at the computer? Thanks alot
I have your Ebook but, I was wondering if you sell them in a regular book?
Thanks again for the great video.
Paul. If we had the second design (one with internal resistor) as stated at 15:00 to 15:30, and there was a short to ground in the signal wire between the connector & pcm. Then we unplugged the connector, then the scan tool would read 0 volts as in the top design and not 5 as you stated. Would that be correct?
+Scott McInnis yes, a short to ground on the signal wire would drop the signal voltage to 0 regardless of circuit design
Sorry for the previous post. What I was going to mentioned just for reference is that most GM vehicles have a 1.47-1.50v reading on the tank pressure sensor with no vacumm or pressure in system. Thanks
Should the resistance values for the FTPS be the same as the MAP sensor?
While testing the MAP sensor with vacuum pump and multimeter, the more vacuum I put on the sensor the more voltage I would read, but on the FTPS tested the same way, as soon as I’d get virtually any vacuum on it it would go straight to full voltage.....is this normal?
@natesmoggdogg Yes it is
For an average home owner that does not own an advance scan tool, can I use a volt meter link in series with a test light and use the reference 5v to test the ground and signal wire. I know that I can do a continuity test to verify ground also but what about the signal wire? Will that damage the computer module?
Step 1: with the key on engine off, measure all 3 wires with your voltmeter. You don't need a test light for psi sensor testing, nor do you need to do continuity tests. Tell me what you have on all 3 wires with voltmeter negative lead connected to a known good ground
Great video, Paul . Is this test done with the sensor plugged or unplugged?
+littlebear gaming Thanks again for your support. Unfortunately I cannot keep up with the number of technical questions I get from my subscribers through email anymore but I have created a forum for you guys for this very thing!
www.scannerdanner.com/forum.html
Thanks for understanding.
Never mind... just read your post below!
i can test someway oil pressure sensor to? shorting out refrains to signal and looking at instrument panel cluster so see going to high pressure?
Quick question:
So I don't have to check for pressure in the system?
My car car 2011 Nissan altima s 2.5.
And I was planning on doing a pressure test first.
I think I'm missing some information. Or I'm not understanding the code.
You didn't suggest it, so now don't know if it's necessary.
Code: p0452 sensor/switch low.
Thank you very much for your videos.
I need to check service info, but this sounds like a tank psi sensor code. And with a circuit low code, you'll be focused on the sensor and wiring and not worrying about what the tank psi actually is.
I was thinking on pressure testing the system first,cause my car after sitting overnight smells like fuel vapor.
Both valves are good and their wiring is good too, including the sensor wiring.
I'm left with the sensor itself. or with an evap system leak .
Can the p0452 sensor/switch low code also
mean .low enough Pressure?
Or is that code primarily to the Pressure sensor?
Thanks again.
Focus on the psi sensor first for that code. I know you smell fuel, which does suggest a leak too, but that system will not be able to run the leak test with a faulty tank psi sensor. So you may have two problems
@@ScannerDanner
Got it.
thank you!
The guy who ran the code reader test , also put my new fuel-pump in , He said the Evap was good , but the code still said PO446 on my 2000 chevy Blazer.. Was he B.S. me.. Is the canister purge valve & vent valve solenoid the same part ?
+Doreen Gotti they are different parts. the vent solenoid is normally open valve that closes when the engine computer tests for leaks and also closes when the purge solenoid is commanded on by the engine computer
nice tutorial but I had one question, what if the signal line and ground are reading at 4.96v like the 5v and signal line? bad grounding?
If your ground is also reading near 5v, then yes, you have a bad sensor ground. These are usually shared with other sensors before grounding through the computer board. Check some of the other sensors and see if they have bad grounds as well, this will dictate your next move. A bad ECM main ground could also cause this issue.
@paulsjunkcars LOL Thanks
What's missing which is very important is where the scanner is plugged in when ref is jumped to signal.....it has to be connected to the PCM?? But where and how?
Through the data link connector under the dash
Good video i have same troble code but only happen when summer is here, i check wires remplace connector, ecm and the sensor still having the low signal from fuel thank pressure sensor, i saw on google the a/c pressure switch it may be affecting. What other possibility can be it??
I am directing all help requests to my forum. Sign up (it's free) and create a new post. Be sure to add a name under "alias" as this is the name that will appear in the post.
Here is the link to the forum.
www.scannerdanner.com/ForumRetrieve.aspx?ForumID=3226
Thanks
Hi can a bad tank pressure sensor cause for the p0449 code? thanks
might be a dum question , when you have a 5-0-0 sensor disconected and
"no wiring diagram" how do recognize wich of the to 0volt wires is what .
(one of the two will have continuity to ground?)
why is someone snoring through the whole video
was there? that sucks
Mark Reyes i thought i heard snoring lol!?. and i thought i saw mr.danner look and shake his head. lol
HAHA! I just watched this with headphones on and yes there is defiantly someone snoring!
I have a 2008 f150 4.2 L and I'm getting a code of P0453. I did some checks and saw my pressure sensor value was NOT moving, so I decided to change it out. After changing it out, I'm getting a stuck negative pressure.
After looking at this video, I attempted to test the sensor, but I'm stuck at determining which are the two wires to jump. I don't know which one is the return signal wire in order to jump it with the 5 volts reference because I'm getting low voltage (millivolts) in the remaining both wires. When I unplug the sensor, I'm getting ~6000 pa. And, when i plug it back in, I'm getting -1760 pa.
Could you help me to identify which of the other two wires have to be jumped and to check the integrity of the wiring circuit?
Thank you very much.
do you have a test light? Use that as your jumper wire, so if you get it wrong the test light will be your buffer against a direct short to ground
@@ScannerDanner
I used a test light on it already to try to determine which one is the ground using a direct positive wire from the battery and found only one wire is completing the circuit. Is that wire a direct ground or a controlled ground from the ECU?
Secondly, why would I get a NEGATIVE reading on my scanner live data when I attach the connector to the sensor and a MAX reading when I disconnect it?
Hi ! a question : I have an Opel (group gm) i suspect an evap solenoid valve fault, only i do not have a fault code displayed on the dashboard. Is it possible to find faults with a pro diagnostic device, which would not be indicated on the dashboard of the car? thank you ! ( Thomas, from France )
Great video! I had the same concerns as others about jumping VREF to signal, just in case the signal wire has a short to ground. Would testing continuity from signal wire to ground be a good enough pre-check? Also would it not be safer to suggest building a 5v power supply tool to keep in your box instead of ever jumping a VREF? Or why not just use a 12v power probe?
Watch my video called Signal Circuit Integrity Update for my Ebook
Also to put your mind at ease with this, the 5v regulator is internally protected by the PCM. You will not fry the reg. if it is shorted to ground. I wouldn't recommend doing so but if you did, once you fix the short it will come back to life. Here are two videos with shorted ref. circuits that came back to life once the short was fixed.
2006 Cadillac DTS Shorted 5v Reference Circuit
2005 Honda Element No Start, No Communication (case study)
I did watch that video, and it is an important update! But wouldn't it be kind of safer and easier to build a tool for supplying 5v without using the pcm's VREF circuit? Think 5v Power Probe. Also what would be wrong with using a 12v power probe for circuit integrity testing? Won't it just show up as 5v on the scantool?
Steve Hulett
You could do that too and I have used a 12v test light for this type of testing and it works too although I would recommend an LED type just to reduce the potential for too much current. And of course the 5v power probe would be ideal for this. I have read, that feature is available with the power probe hook?
ScannerDanner
You're right about the Power Probe hook! Sweet product. It lets you supply between 0 and 5 volts in 1/2 volt increments. That's pretty handy since it lets you adjust it to a level low enough to not even trigger a fault code for out of range! It also lets you send continuous or pulsed voltage. Well, here...
www.powerprobe.com/hook.php
I did the same test on a oil pressure switch while looking at data jump the wires I got my 5 volt but my pressure reading stay the same any advice will be helpful
Sometimes the scan tool will not update values without seeing and RPM signal.
Hello Sensei. I know this is VERY long in the tooth, but it remains such an excellent reference -- I'm HOPING.... (that you'll see this - and can drop a HINT???)
I've an 05 MB E320 that's failing smog cert because of a recurring P0453 - FTPS signal TOO HIGH. Neither of my scanners (iCarSoft MB II and BlueDriver) will allow me to monitor that signal, so I tapped into that wire so I could monitor the voltage with a DVM. Initially I was seeing about 2.5v, then later (as the day got hotter?) I saw about 1.5v. Fine, I thought - so WHERE is this TOO HIGH thing coming from? Well, here's the reason I'm halting my own edumacation via your videos to ASK:
This signal line has been showing me (virtually) ZERO volt diff to the ground line (0.001, actually). so I am BAFFLED! Should I be baffled, or should I know that this actually MEANS SOMETHING?
FWIW - I do not have what you refer to as a 5-0-0 circuit: mine reads 5-4.97-0 - so I conclude it has the internal resistor.
I never know what to expect (for the voltage level on that signal line) - it sometimes shows me that (reasonable) 2.5v reading - until I look away and then look back. It's MESSING with the vacuum level in my skull!
Great info so far! The 4.97 is your signal.
I would monitor that signal wire at the ECM connector while your driving it. That high voltage code is suggesting an intermittent open in the signal wire or the sensor ground. Or a faulty sensor. But you're going to see that signal voltage rise to that bias level as the open is occurring. You may not see the full 4.97 either, but it's going to seriously mess with those voltage levels and in the opposite way when measuring at the sensor, that is if our open is on the signal wire. If our open is on the sensor ground, it will measure no different at the PCM and Sensor.
Lol I'm rambling
@@ScannerDanner I am humbled and honored that you bless me with your time to answer - and so promptly, to boot! As it happens, I did find that I CAN read the voltage at the PCM (with my iCarSoft MB II) so I believe I CAN complete the homework assignment. It occurs to me, however, that I might need to confirm the best place to connect the ground lead of my DVM: as it stands it's on the ground wire of the sensor wiring; but I wonder if I shouldn't oughta move it to a chassis ground instead? Or perhaps connect another DVM with its positive lead on the ground wire of the sensor wires and its ground lead to chassis?
Anyway, in advance of this next test session (while I'm driving to return the sensor I bought - which doesn't fit) I might offer this near-useless tidbit: I was already leaning toward suspecting the sensor failing - and your comment tends to confirm my weak intuition that way.
But - according to an obscure corollary of Murphy's Law - the thing will behave just fine - as long as I am LOOKING at it. But as soon as I look away..... I mean - what are the odds that I'll happen to be looking at it WHEN it exhibits its little quirk? I'll give it a go, though.
Thanks again!!!
@@YahWho-is1tt yes, battery ground when possible. Sensor ground is okay, only when you want to clean up a noisy signal on a scope. Other than that I never use sensor ground when troubleshooting something like this, because sensor ground could be one of the problem areas! It should read .1v or less on that sensor ground when compared to battery ground, with the circuit loaded (Key on or engine running)
@@ScannerDanner Well, yesterday's driving experiment has thoroughly confused me! I drove about 75 miles in three major stages (IOW made 2 stops of about 2 hrs each). Watched voltage at ECM/PCM with scanner and on signal wire at sensor with DVM. NEVER did I see any significant discrepancy (aside from tiny fractions and slight reactionary time differences. At start of drive the voltage was about 4.85, but it immediately started dropping slowly - was down to about 3.6 by stop #1, and about 2 after stop #2 - which was heading home. Down it continued, until it was down to 0.02v (which corresponded to -60 mbar). I thought perhaps the consumption of fuel was creating more of a vacuum inside the tank, so I stopped and opened the gas cap, but when I did I heard/felt NO sign of vacuum as the seal broke. Nor did that make ANY difference in the voltage reading. What DID happen at that point, though, was the CEL came on with a DTC of P2012-000, NOT the P201C-000 that has been plaguing me (causing the smog cert failure). So I'm getting codes pointing at both the tank pressure sensor AND the charcoal filter valve/solenoid. The latter I have not yet examined - but I was told to check the wires for rodent damage.
I also read that the EVAP system test does not run until a full tank has been run down to about 3/4, which is ball-park close to where the voltage dropped to nil - but that is merely a long-shot guess on my part at this point. Does that slow, steady drop make any sense to you, by any chance?
I have a new sensor, but its electrical connection does not match that of my ?OEM? one, so I am waiting for the necessary adapter - at which time I can (hopefully) replace the suspect sensor (with a tricky surgery - as more than the elec jack is different!) Wheeeeeeee - such FUN! (as your tab continues to grow....)
Oh well…. Guess I resort to throwing money and parts.
Can bad FTP sensor cause poor acceleration?
No sir, that is for EVAP leak detection only
AN IN THE 5-0-0 SYSTEM INSTEAD OF A JUMB WIRE WE PUT THE TEST LIGHT TO BATTERY POSITIVE AND LOOKED AT THE DATA WE WOULD NOT SEE THE INTEGRITY OF THE WIRE? THE SIGNAL WOULD NOT GO UP? WE DON'T HAVE A PULL UP SYSTEM?
That would work, but I'd suggest you jump the 5v ref to the signal wire with the test light, instead of going to battery positive
@@ScannerDanner BECAUSE THE TRANSLATION IS WRONG TELL ME WHICH IS CORRECT 1)JUMB SIGNAL AND REFERENCE WITH TEST LIGHT? 2) CONNECT THE BATTERY POSITIVE TO THE TEST LIGHT AND DO WE TOUCH THE SIGNAL?
I can hear someone snoring. Was that Kenny? j/k
Could a bad pressure sensor give you a no flow code p441?
what is the definition of the P0441 code?
@@ScannerDannerThanks for responding.. The snapon scanner says Evap system incorrect/no purge flow.
I'm stumped on this and i don't have a garage. So trying to diagnose this outside sucks. Its really cold up here in ny lol.. maybe you can pin point me in the right direction.
I'm working on my friends 2005 kia sportage 2.7L auto 4x4 with 90k miles.
Im trying to pass inspection but i can't seem to figure this out. I replaced both the purge and vent valve and the same code keep comming up. Also idk if this might help but my friend told me when he fills it up, it becomes a crank no start, so he never fills it up all the way and its fine as long as he does that.
I checked the FTP sensor on the scanner and its reading zero hg. Im not familiar with the evap system so much or what kind of readings the FTP sensor should be. Can it be a faulty FTP sensor or
clogged charcoal canister?
Thanks, Pablo
@@pablomarquez4431 I just did a Hyundai (same exact electrical system) with an aftermarket purge valve causing large leak codes. I wouldn't be surprised if your issue is being caused by an aftermarket purge valve. It MUST be a bosch purge valve (bosch is who makes the valve for the factory on these) Here is the link to the final part of that series th-cam.com/video/ipTSsmZhZxo/w-d-xo.html
I know this is an old video, but have you ever seen a P0451 on a Ford Pickup? mine is a 04 5.4l F150 Lariat. I have looked at the sensor and grounded the signal and the voltage went to 0 and took the 5v to signal and got 5v. The voltage changes but I guess not enough. Suggestions on how to proceed?
What is the definition of the code?
Hi there sir I've got a 2011 silverado it's throwing a p0449 code I changed the evap vent solenoid and it still comes back on the vent solenoid is clicking when the vent solenoid is hook to the charcoal canister I can't put fuel in it but I can when I disconnect the line from the canister will a bad tank pressure sensor cause that
What do you mean it's clicking when connected to the canister?
@@ScannerDanner it clicks when I hook the wire connector to it
@@shannoncarroll3600 okay, it absolutely shouldn't be doing that and that is why you can't fill your tank. Your control wire is shorted to ground or the ECM driver for that vent solenoid is shorted. Do a really good visual on that harness!
@ScannerDanner I mean it only clicks when I unplug the wire and then when I plug it back in it clicks
@@shannoncarroll3600 I understand and it shouldn't be doing that. Your control circuit is shorted to ground
What if the signal short to ground and i jump the 5 v ref to the signal it mean i jump it to ground ??
Great question! You would be shorting the 5v ref circuit to ground.
What would happen as a result? You'd lose scan data as the ECM would stop communicating (on a single 5v reg system)
As soon as you take your jumper off and cycle the key the 5v would come back.
I've modified this test in later videos and suggest using an incandescent test light as your jumper wire so as to act as a buffer if the signal wire is shorted to ground.
@ScannerDanner Yes, in addition, I looked at the internal structure of the power supply system, which is an integrated circuit (buck converted ). Able to deal with situations such as short circuits. Thank you so much, Mr Paul