What can cause an O2 sensor to read near 5 volts? (Chrysler bias voltage)
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- เผยแพร่เมื่อ 4 ก.ย. 2024
- This video applies to all Chrysler, Dodge and Jeep vehicle.
Why is there 5 volts on an oxygen signal wire on a Chrysler?
Is this normal or does this mean there is a problem?
I will answer these questions in this video.
Engine Performance Diagnostics chapter 5 pages 11-18
Tests shown:
- how to use the oxygen sensor bias voltage to determine oxygen sensor heater activity
- how to check the signal wire for opens and shorts to ground using bias voltage
- how to use your body as a resistor for testing the oxygen sensor circuit
- why connecting a digital voltmeter will cause a drop in scan data signal voltage
Tools used:
- scan tool
- lab-scope
- jumper wire
- back-probing tools
- digital voltmeter
Related videos:
- Engine runs rich P0172, P0175 from a blown O2 heater fuse
• System Too Rich P0172,...
- Oxygen sensor operation and testing (preview from ScannerDanner Premium) • Oxygen sensor operatio...
- Oxygen Sensor quick tests (bias voltage)
• Honda Oxygen Sensor qu...
Playlist
- (Chapters 4 and 5) Fuel Trim and Oxygen Sensor Testing
• (Chapters 4 and 5) Fue...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
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Disclaimer:
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Paul came to my house to buy a fridge and kindly spent 20 minutes diagnosing my 1990 volvo wagon which would not start. He explained that I needed a new ignition coil. I bought a used one on ebay for $20 and voila! Problem solved. My mechanic ripped me for $300 and still could not find the problem. Wish Scanner Danner had a shop. Thanks!
I don't work in automotive but I've done some investigations better than the service guys just with what I learned on this channel. I just had an ECU swap investigated by me. The service found a bad relay and a coil and I insisted to find the cause. I used a check lamp and noticed constant power from the ECU to the coil (I assume shorted MOSFET). After the ECU swap I got a "short to positive" on a oxygen sensor and the service wanted to change it. Again, they did not agree it is a strange coincidence to have that sensor broken right after the ECU swap. I went home and found a bent pin in a socket on the ECU. Problem solved. Thank you for these awesome videos!
That's what I'm talking about man. Awesome!
I've been watching your videos for years and this pops up when I search for shorted to voltage. It's my grandparents 98 Ram and you describe the symptoms exactly. Thanks for the help.
Awesome!
The time I know I understand the material in these videos is when I am repairing a car that takes its sweet time setting O2 monitor. Super info!! A really neat test is using the low amp clamp and watching current flowing to the heater circuit. Looking at the book and then linking the appropriate video.
Good one, I've been doing this a long time and still learn a lot from your videos .
it could go either way. 451mv is rich and 449mv is lean. That is how tight this number is. i have seen a negative 30% fuel trim from an 02 fixed at 451mv.
thanks for your comment on my book!
For the most part yes. However some manufactures are using the downstream O2 for minor fuel trim corrections. I've never seen it, but I have read about it. As far as troubleshooting goes I have NEVER seen a downstream O2 cause a driveability or fuel trim trouble code.
Nice class. I am translating your book while I watch the videos of the links that are there. I hope to finish it soon.
From Peru. Thanks
@gvanaski Nice! Thanks for the reply. I am glad it worked out for you. And thanks for the fridge.
I don't see those anymore, but they did have a higher voltage signal, not sure if I would call it a bias on those. It was more like a thermistor circuit in its design. So it used a 5v reference, not a bias.
Yesterday, i was working on a dodge caliber 2.0 it had a code regarding "Actuator Flow Control Valve high voltage p2017" and i found the same 5v bias voltage on the signal wire what I thought in the beginning it was a short to 5v reference circuit, my next step was to connect a meter to 5v ref on the same connector, fully ground signal wire with a test light, it did not lit, 5v ref was intact, old code was stored / a new code popped up it was "low voltage" , went an extra mile and connected the meter in conjunction with the test light and it was fixed 0v, i remembered watching this video last year so i was sure it must be a bias. Thank you for spreading the knowledge
This video was AWESOME!!! Have been dealing with a high voltage 02 code on both sensors. Would constantly stay above 1 volt. Run great @ higher rpm and terrible idle. Heater fuse was blown. Runs great now, and it all makes sense!
Which is the heater fuse?
@JUDGERAMBO Not at all! This is not a typical 5v reference you would see to a MAP or TPS (which you would never jump to ground) On this design the 5v ref. goes through a current limiting resistor before it leaves the computer. If you notice in the video it is so weak that I can pull the 5v down through my body. Can't do that on a regular 5v ref circuit.
Hi brother Paul. Been researching titania oxygen sensors and learned they use a 5 Vref because they can't produce their own voltages like the zirconia oxygen sensors do. Titania oxygen sensors change resistance depending on amount of oxygen present in the exhaust stream. High concentration of oxygen will cause this sensor to have high resistance. This will result in the sensor signal to be high. Low concentration of oxygen will cause this sensor to have lower resistance. This will result in the sensor signal to be low. With this in mind, start watching the sensors reaction at the 2:49 Mark of the video. When the assistant let off the throttle. The decel fuel cut makes the system lean, and the exhaust goes lean. The scan data shows the signals go to 1V.
This is a zirconia O2 my friend. I am familiar with the titania sensors and they were used on some older jeeps but not here.
The 5v bias circuit on these is different than the 5v signal on the titania sensors. They were built more like thermistor circuits.
@@ScannerDanner at the 2:49 mark of the video, when assistant released the throttle, the voltage went up. Not sure how to understand this if it was zirconia oxygen sensor it should have gone down in voltage. Have a blessed and safe week to you and your family.
@@billyyoder8171 voltage went back up because the sensor was too cold with the heater not working. This a bias signal voltage that you are looking at. Night and day different than the signal voltage on a titania sensor. On the 5v bias that a zirconia uses (chrysler), I can use my body to pull the signal voltage to ground, on a titania 5v signal, you absolutely can not.
OXYGEN SENSOR (O2S) MONITOR
Effective control of exhaust emissions is achieved by an oxygen feedback system. The most important element of the feedback system is the O2S. The O2S is located in the exhaust path. Once it reaches operating temperature 300° to 350°C (572° to 662°F), the sensor generates a voltage that is inversely proportional to the amount of oxygen in the exhaust. The information obtained by the sensor is used to calculate the fuel injector pulse width. This maintains a 14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio, the catalyst works best to remove hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxide (NOx) from the exhaust.
The O2S is also the main sensing element for the Catalyst and Fuel Monitors.
The O2S can fail in any or all of the following manners:
slow response rate
reduced output voltage
dynamic shift
shorted or open circuits
Response rate is the time required for the sensor to switch from lean to rich once it is exposed to a richer than optimum A/F mixture or vice versa. As the sensor starts malfunctioning, it could take longer to detect the changes in the oxygen content of the exhaust gas.
The output voltage of the O2S ranges from 0 to 1 volt. A good sensor can easily generate any output voltage in this range as it is exposed to different concentrations of oxygen. To detect a shift in the A/F mixture (lean or rich), the output voltage has to change beyond a threshold value. A malfunctioning sensor could have difficulty changing beyond the threshold value.
OXYGEN SENSOR HEATER MONITOR
If there is an oxygen sensor (O2S) shorted to voltage DTC, as well as a O2S heater DTC, the O2S fault MUST be repaired first. Before checking the O2S fault, verify that the heater circuit is operating correctly.
Effective control of exhaust emissions is achieved by an oxygen feedback system. The most important element of the feedback system is the O2S. The O2S is located in the exhaust path. Once it reaches operating temperature 300° to 350°C (572 ° to 662°F), the sensor generates a voltage that is inversely proportional to the amount of oxygen in the exhaust. The information obtained by the sensor is used to calculate the fuel injector pulse width. This maintains a 14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio, the catalyst works best to remove hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxide (NOx) from the exhaust.
The voltage readings taken from the O2S sensor are very temperature sensitive. The readings are not accurate below 300°C. Heating of the O2S sensor is done to allow the engine controller to shift to closed loop control as soon as possible. The heating element used to heat the O2S sensor must be tested to ensure that it is heating the sensor properly.
The O2S sensor circuit is monitored for a drop in voltage. The sensor output is used to test the heater by isolating the effect of the heater element on the O2S sensor output voltage from the other effects.
@tyroauto1 I am on the OEM side. I have a couple of pages in my book on this. I'll send you a sample later. And yes you are correct, it will read differently on the Global side on some.
I'm Having A P0056 Code Bank 2 Sensor 2 Heater Circuit. 2002 Chrysler 300M special. I have Swapped My O2 Sensors And the code is Still there. The Code Falshes and Comes On as soon as I turn the Ignition before even starting the Car. Notmally the o2 sensor codes come on after driving the car and the computer takes some cycle data, But I Unhooked the Battery and soon as I turn the Key the Code Flashes. I suspect I dont have voltage at the Pins, But Idk which ones are the Heater wires, I traced the 2 Black/White wires on the O2 Sensor to the Pins they Connect to and got 2.3mV with key on engine off (do I have the correct pins?).. I'm Wondering if I have to Start the Engine for the correct voltage to show Up? And I understand that I should be looking for 12V?
Another awesome video. I always learn a thing or two from watching your channel. One question I see that you have used an AES Wave one channel scope. Can you recommend any two channel scopes. AES has one, four and eight channels.
Thanks.
2012 Jeep Wrangler- My bank 2 downstream sensor was throwing a fault, so with 130k miles on my jeep, I just went ahead and ordered a whole set of NTK o2 sensors and replaced them. The same sensor is still throwing a p0158, and I verified that the voltage is stuck at 1.275v. I ran some Catacleaner through the jeep to see if it would help at all, in case the cat is clogged, but it didn't make the slightest difference.
I'm not sure where to go next with it. I had replaced the spark plugs at 80k miles with factory Iridium plugs, which would only have 50k miles on them now.
Broken wire maybe on that circuit. Take some direct measurements for me at that sensor with engine running. The two whites are the heater circuit and the black is signal and gray is signal ground.
@@ScannerDanner Me and my buddy put a meter on it yesterday and were able to verify the heater wires had power, but not the others. We started at the harness connector and worked our way back and found a broken wire. No idea how the wire would have got broken, since it is not physically in contact with anything else. It is about an inch and a half back from the connector, so not as bad as it could have been.
@@wvjeepguy8178 heck yeah man, nice find!
Thanks for your excellent videos! The use of bias voltage, is that typical for titanium O2 sensors?
on the sensor side the heater wires is brown, tan is ground and purple is signal which reflects a ACDELCO brand. On the ecm side brown is signal, black is ground and the heater wires is purple/White and tan/white. When connected I verified each wire was matched to do its job. The volts reading I gave you was on the ecm side, car running and connector disconnected.
+Sonyman34 nice description! lets stay in the same thread from this point on. It is easier for me and others to follow.
Okay, you definitively do not have a bad computer. Let's re-do those two heater tests with it plugged in and back probing the connector. Also make double sure that your voltmeter has a good ground for the test.
That voltage is too low on the feed and too high on the ground, but it was unplugged and unloaded.
+ScannerDanner On a 98 Sunfire 2.4, I am showing a single wire upstream sensor and a 4 wire downstream so I assume we are dealing with a downstream problem. That downsream O2 heater is grounded to the block (left front of engine) and is powered by a fuse "O2 heater fuse" 10amp in the fuse box.
This engine is notorious for ground wires to break inside of the insulation right at that ground eyelet on the block. It is the same ground location as the battery negative cable. If you tug on them they will pull apart. But do those voltage measurements first.
+ScannerDanner probed on ecm side heater wires, harness plugged in, car running. Volts on both wires 5.02v. Multimeter set on 20V. Moved around ground wires on engine block and installed jumper wire from ground at harness to negative on battery, no change both times.
yes. very common for a bad sensor to react like a bad heater
Down stream 02 should not affect fuel correct. Maybe I interpreted what you said in the video wrong.
@beefystik Rosedale Technical Institute in Pittsburgh Pa
Thanks for you kind words!
Paul
ScannerDanner. I have an 02 grand cherokee4.7 I'm getting high voltage codes downstream o2s do these work off the heat from the exhaust . As mine are not in the pipe.
@@whysolong27 yes and no. It does have an electrical heater circuit too. High voltage codes are from the bias line not pulling down (from a hot, working O2). So heater circuit fault (sensor or wiring) or from a dead O2 signal circuit
@@ScannerDanner ok so I'm lost. checked power checked ground second set of o2s and I'm still getting p 0138 p0158
@@whysolong27 2nd set of O2 sensors? are you using the correct ones?
th-cam.com/video/-lUYRqaYvYI/w-d-xo.html
@@ScannerDanner as far as I know NTK brand down stream o2s it's what rock auto had for my year and model and local parts store . I'm getting both down stream codes for high voltage circuit to high. my engine has been professionally tuned.
2007 ram v6. Fighting entire bank 1 going -25 long term at idle and all bank 1 cylinder misfiring. Obviously bank 1 sensor keeps popping high code bank 1. New sensors customer even had ecm replaced. Fuses are good. I typically like a challenge but this truck is getting to me.
What is bank 2 showing? How does it run at WOT
@@ScannerDanner bank 2 is 6.2 and the faster you rev the less you can tell it’s missing but have not driven it with scanner hooked up. Will tomorrow. Thanks !!
Great Info!! What side of the computer are you on, Global or OE?? With the Dodge pickups I seem to get different readings depending on if I'm in Global or Oe??
can that cause random misfire ? am getting code for the O2 sensor circuit high voltage and getting random misfire also getting p1148 1 closed loop 2 closed loop bank 1
Excellent Information. Thanks. When you say wide open throttle, do you actually mean pedal to the floor? Or does that just mean normal operation when driving under a load?
Pedal to the floor my friend
I have a 2000 ram 5.9 runs excellent idles smooth starts right up the only thing is that under load the exhaust manifold glow red I have replaced the O2 sensor dropped the converter and Muffler and tested and still they glow red meaning to manifolds replace fuel injectors and they still glow red on a scan to a while you're driving everything is reading and range but still exhaust manifolds glow red no check engine light timing was off by a little bit but not enough to affect anything any help would be appreciated as I am frustrated in this
Can this happen with a blown ASD /Fuel fuse as well? Have an issue 2005 PT Crusier... battery is fine, I replaced ASD relay and up stream down stream engine light stayed off for 160 Mile's back on for low voltage I haven't checked the ASD/Fuel fuses yet. S.O.S.
Would there be a problem if the 5v was jumped to ground directly insted of "through the body"?
hi,i love your teaching danner and i just wanna ask about my bmw f30 when i checked O2 sensor upstream is 1.45V and dowstream is 0.64V that is problem with up stream sensor right? and the car does not show checked engine light?
Sounds like a wideband upstream sensor and most likely not an issue
@@ScannerDanner thanks i will research about wideband O2
Why does your body or a test light pull to ground and not the O2 sensor plugged in? Doesn't O2 have resistance to pull it to ground when cold?
okay I see where you mention the sensor does have infinite resistance when cold.
I think I have this exact issue on a 2007 300c.
P0138 and P0158 voltage errors on both downstream. Brand new sensors.
Which relay did you remove is this video?
Trying to work out exactly what my next steps are.
Thanks
Did you fix it?
@@repeater95 yup
New sensors (aftermarket) were faulty.
Hooked them up to Appcar while driving and the voltage never dropped.
Bought some OEM sensors and has been fine ever since.
@@bigblockheed nice, you are lucky, I change mine oem and the fault persist
Code P0141, GM 98 Sunfire 2.4L, New ACDELCO HO2S, fuse good, wiring checks out, suspect the ecm. How can you tell if the ecm is the problem if a pocket scanner says O2 heater check OK?
+Sonyman34 what are your voltage readings with the car running on the two heater wires?
4.98 volts Tan/White wire, 4.56 volts Purple/White wire
+Sonyman34 Those aren't right. Give me the 4 colors of the wires on the sensor side. Is it two whites a gray and a black or Two blacks a white and a blue or what? The heater wires are always the same color on the sensor side. Measure those two wires. (same color sensor side of the harness)
This voltage runs through the signal wire or the return signal wire? Is it normal to have voltage in the return signal wire?
Im having problems diagnosing two codes p0132 and p0152 in a liberty 2004 3.7,already changed both upstream o2 sensors, If i drive the truck they start to vary but once I stop in the traffic the sensor go back to 5 volts, do you think my pcm is bad?
Nope, I think you used the wrong O2 sensor th-cam.com/video/-lUYRqaYvYI/w-d-xo.html
th-cam.com/video/gtTKOuu6EPw/w-d-xo.html
The short reason is that the heater circuits are cooling off more than they should be because the sensors you put in are designed for constant current flow, not a pulse width modulated heater like your Jeep uses. You MUST use a factory sensor. They are made by NTK (a division of NGK) and you can find them outside of the dealer for a fraction of the cost.
@@ScannerDanner i replaced both o2 sensors with mopar oem parts, part number 56028994AA. thanks for the response.
@@ScannerDanner i forgot to mention , i checked the harness from the pcm connectors to the o2 conector harness , everything is okay, no variation when i move the cables, checked with a osciloscope the function of both o2 sensores unplugged and seems to be ok the readings, the problems start when i connect the o2 sensors to them harness.cheked resistance in the cable , everything in the harness its okay. thats why im thinking of a bad pcm.
Does that pertain to the 4 cylinder also
Absolutely! It has nothing to do with the number of cylinders.
Will the computer still pull fuel away from both banks if say the problem only relied on B1S2?
generally S2 O2s (downstream of Cats) are only used for Cat and S1(upstream of Cats) self testing, never fuel control, they can only set codes for an upstream O2 (S1) or Cat codes as that is their main purpose.Note that as far as I am aware fuel control is NOT ever done using a DOWNstream O2 (S2).
What does it mean if you have an upstream o2 sensor reading nearly 5v already replaced the sensor 06 Chrysler Pacifica
Can you make the signal voltage drop by running the engine at 2000-3000 rpm in park? If yes, you have a heater circuit issue. If no, you have a signal circuit problem. Let me know and we'll go from there.
Did you solved?
I have a 2007 dodge ram 1500 with the 4.7L v8 in it. I am having an issue that I am hoping that someone with more knowledge can help me with. I recently got the code p0430 check engine light come on in my truck. The code is for inefficient catalytic converter bank 2. after talking to multiple sources and doing research, everyone said that there is a 90% chance that the converter is bad and would need to be replaced. I replaced the converter and the code came back on the same day. I furthered investigated this issue by using my scanner and looking at the voltage of the 02 sensors on both banks of my exhaust. When I did this, I noticed that my downstream sensor on bank 2 was acting weird at start up and while driving it. The downstream sensor has the same voltage as the other sensor before I start the truck, but once I start the truck the sensor loses most of its voltage within a minute or so. Sometimes the sensor with show 0.035 or so volts but nothing compared to the same sensor on bank 1 which is .685-.7 ish. When I drive the truck on the interstate the sensor will sometimes show flashes of it working......if I accelerate on the throttle it will jump up and match the bank 1 sensor 2, but then it will fall back down. The upstream sensor is working in the same fashion as the bank 1 upstream sensor so it can not be that sensor causing the issue. I figured that I have a bad 02 sensor since I am losing voltage at startup so I replaced the bank 2 sensor with a new one. I drove it on the interstate and it still did the same thing..........the check engine light did not come back on but it did same "pending code" on my scanner and it was the same p0430 code.....
It is now clear to me that there is a communication problem with the pigtail that connects to this sensor. There is either a problem with the computer on the truck with this sensor (which seems unlikely to me since all of the other three sensors work) or there is a problem with one of the wires going from the computer to the pigtail. It does not appear to have any cuts or burns in the wires as far as I can see.
I am not sure what I need to do next.....I do not know where/how to test the wires or see where the ground is for the pigtail. I have tried to find more information but have had no luck. I do not want to take it to the dealer and pay a lot of money to just have them look at it....they will probably assume its a bad computer and charge a lot of money to replace it..
Some help in the right direction would be great! Thanks so much!
Justin if you put and aftermarket converter on there most likely that is why your getting your code I would strongly advise you to buy scannerdanners book and get his premium channel it will make you understand everything and be really efficient at fixing cars and you won't be a parts changer good luck
High Paul love your book, I'm in section 4 right now which led me to this video. Im just wondering if a GM O2 sensor with a 450mv bias and blown heater fuse would cause a false rich condition like the Chrysler 5v bias? Got to say your book is the BOMB, Im talkin little boy and fat man status.
Paul came to my house to buy a fridge and kindly spent 20 minutes diagnosing my 1990 volvo wagon which would not start. He explained that I needed a new ignition coil. I bought a used one on ebay for $20 and voila! Problem solved. My mechanic ripped me for $300 and still could not find the problem. Wish Scanner Danner had a shop. Thanks!