Lexus Crank No Start and Keeps Blowing Fuse DIY Diagnosis
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- เผยแพร่เมื่อ 27 ส.ค. 2024
- My neighbor's 1995 Lexus SC400 will not start and he states it is because it keeps blowing a fuse as soon as ignition is turned to ON. Can we use a scientific approach to find the issue without firing the parts cannon?
Yes it is all in the diagnosis... .your train of thought is good without even using a short finder and you're absolutely right, it never gets old getting it to run 👍
For future reference, if you plug a headlight bulb into the fuse socket using small terminals, you will save on sacrificial fuses. The headlight bulb draws enough current so it won't burn wiring. Headlight bulb on - short to ground exists. Headlight bulb off - short to ground doesn't exist.
Thanks for that tip!
Same technique can be used with a test light. There is no need to draw too many amps by using a high amp bulb and it will drain the battery faster as well. If you have a battery charger then that's not a problem but most people probably own a test light.
Yup. Circuits need a load in order to not be short to ground. Doesn't matter what kind of bulb it is, it just has to complete the circuit. Then you can sort from there. Unplug your easy to get to components and see when the light turns off. Note your ohms law comes into play with intensity of the light bulb and resistances in the rest of the circuit. After a blown fuse repair, I always check current through the circuit with an amp clamp to make sure it's correct.
You can also use a buzzer or horn as a load if you are working somewhere where a bulb load can't be seen.
Nice tip. Just one small correction on what's happening. It's not that it "draws enough current". It's that the resistance of the filament is high enough to limit the current in the circuit to a safe amount so as not to cause damage to the rest of the wiring. Ditto with a tester or anything else you put in the circuit that's designed to work on the native 12V in the car.
You are the man Matt! Now back to video!
Honestly, even though these videos are very informative and helpful with automotive diagnosis, the thing I get the most from these videos is an opportunity to experience the entire journey from problem to thinking to troubleshooting to solution. It always leaves me feeling better about working through a problem, either automotive or otherwise- it's always a great boost when I'm in the woods struggling to get my bearings!
thanks! Yes the process has nothing to do with automotive actually- it applies to ALL problems in ALL disciplines-- even “life” problems.
IT STARTS! Cracker Jack troubleshooting skills. I worked as a aircraft electrician during the 70’s kc-135’s, F-4’s, c-130’s, T39’s, Helicopters coming from Vietnam. Space or the lack of it was an always an issue when working on aircraft, decades old age and hard duty but I loved it all especially the a-hah moment.
One of my secrets revealed. Getting closer to a culprit/answer/etc. by dividing by two in my industry is called Successive Approximation. From 100 possibilities you get closer to the answer fast: 100, 50, 25, 12, 6, 3, 2, 1 so if you had 100 possibilities you can figure out the source in just 7 steps at the most.
I love the math on that!!
The "20 questions" logic is spot on. For diagnostic purposes, use a test light as a replacement for the fuse...it is self limiting on current draw and will light if there is a short, making diagnostics for a short much faster (and cheaper) than continually replacing fuses. When light is out, you eliminated the short.
Big man, you have no idea how your videos has helped me as a young auto engineer. Since I start following them my skills has impressive improved.
glad to hear it!!
Dear Eng. Matt, also and for your ease as you may aware there is a device named "automotive short finder tool" or "automotive open circuit finder tool" where you can feed 12V electricity to one part of the circuit and track the electricity through the wiring harness till you reach the shorted or cut end. It is also very handy for house circuitry. Its price through ebay ranges from $ 30 to over $ 100. Oh, By the way, maybe later on you need to find a land lot or a house with a big land so you can build a sort of prefab warehouse on a concrete slab with at least 6 meter wide by 6 meter length and 5 meter height where you can put inside a car lifter where that would be a vast playground for such a great hobby, but I shall warn you never to do it unless you have the financial capability to do so without ever involving in any sort of loan, like if you have a multiple rental properties that yield you a stable income of 6 or 8 K / month after overhead expenses, in addition to your career work in engineering field (a cash flow dream Lool), if not, then play small Loooooooool. Enjoy your Heaven. John Jack Kaplanian from Jordan, Middle East.
"A Fist Full of Fuses" A sensible, pragmatic automotive diagnostic video filmed in the West starring a Clint Eastwoodesque scientist and automotive enthusiast. Does he feel lucky?
The script and story are fine, but still needs some western styled theme music and a clip of the car driving away in the sunset.
Nice diagnostic. Thanks.
hahahaha I was I thinking I should come up with a reference to that when I said it but your idea would have nailed it. I totally should have done a montage or something lol.
Another great video. To borrow a phrase it never gets old seeing your methodical approach to diagnosing the issue. And no worries about the garage. If you see a tidy garage it usually means it's not being used enough.
oh I am doing something about the garage! ;-)
Awesome. I know this is an older video. But helped me on my son's 2001 lexus IS 300. It was blowing the EFI Fuse and ended up being an oxygen sensor melted wire. Appreciate the info!!!!
Wicked video I hate electrical things but watching your videos gives me the confidence to have a go, Thank you 👌
Hi. I just want to say You and ScannerDanner are making the lives of mechanics much easier. Thank you masters.
Our pleasure!
It's always a good day when a new Schrodinger video pops up - and this one is no exception. I'm sure your 'divide by two' method of eliminating variables will instantly inspire a plethora of time-saving diagnoses.
And what a time to go sporting a half-beard! Granted it looks better, but my cellphone tells me it's currently -4° in Denver - what were you thinking? Hahaha.
hahahaha I trimmed the beard before I knew an arctic blast was coming lol!
Always impressed by your thorough explanations and strategies. You're a great teacher Matt!
I appreciate that!
I wonder in the schematic there must be a common junction connector to separate the different circuits that run off that fuse. Perhaps taking a multimeter and unplugging the junction and test the different pins for grounding.
Thank you very much for the videos and some of your responses over last Christmas.
I always look forward to/learn something new from your uploads. GREAT content!
They make resettable breakers for some of those if you do a lot of blowing fusee issues it worth having. I love watching these kind of videos. For some reason I haven’t been showing in my list. . Great video.
Fantastic method and explanation for narrowing the problem down.
I love the way you diagnose the problem. Then the way you explain it. Totally understandable. Thanks.
You are so welcome!
A Leo Tolstoy's "work as a reward" in flash. MAESTRO.
The technique you describe is called a binary search, and yes, it is tops.
good job Matt. nice find hopefully we can see more video like this one
I learned that technique through Scotty Kilmer which is what I call test and eliminate or subtract. I apply those same principals to others thinks such as repair computers. As a former Computer Reapir Tech at a local Computer shop, I had a customer bring in a custom built PC with blue screen error code Memory management. The most logical think I did was to pull all the RAM modules except one and then start the computer to test the RAM module. I repeated the same steps for each RAM module until I found the bad one. Only 1 out if four were bad and I replaced it.
I believe this vehicle does have OBD2 diagnostics but the interface for the scan tool was not standardized yet...proprietary to Toyota.
oh that’s probably right- I have run into a few 95’s that had OBD2 but it’s been so long I forgot about that. I should try that out.
The 1994 Toyota Camry with the 1MZ V6 was one of the first, if not first, Toyota that had OBDii...which I own. But I cannot read the codes as the interface is not standard. What you shared is still very useful...just correcting that it is NOT oBDi. On electrical circuit issues with cars, only 2 possibilities...an open or shorted circuit.
Great work Matt using logic, especially that troublesome O2 sensor harness which finds its way into a pinch!
Good to see you again!!
Had the same issue on a Chaser 1JZ, local guys tried everything, according to them, even a different ecu, and guess what, it was an open wire on the 2nd O2 sensor touching the exhaust....
Excellent troubleshooting.
Thank you very much again thank you for helping your neighbor pretty cool man another fantastic video no surprise thank you👀🌿
Thanks again!
@@SchrodingersBox Hi Matt thank you another question how can I get to your pay channel?
it’s at www.Schrodingersboxqm.com.
“If that doesn’t show up then I suck at filming”. LOLOLOL!! Good one! Nice diag and very satisfying for us too! I call that diag process the 50% Process - decouple half the variables. The only thing you missed was explaining the rest of the process to the end if the culprit is at the END of the trail, not within the first 50%, I.e., next eliminate 50% of the remaining suspects, etc.
That was educational, entertaining and inspiring. Watching your video made me forget about my own project, but I learned a lot about the process needed to fix mine. You just gained a subscriber. Thanks.
Great to hear!
Hi Matt, AWSOME approach and always good to see you up loading videos cheeeeers.
Thanks J!!
Perfect video for valentine's day evening, awesome catch Matt!
Great tips! This happened to me too. Years ago I couldn't get my car to start after changing an intake manifold gasket, it kept blowing the ECU fuse as soon as I turned the key on. Unplugged everything on that circuit and still had the same problem. The problem ended up being that somehow one of the fuel injector wires got pinched between the fuel rail and one of its mounting studs during reassembly, shorting it out.
that would do it!!! yeah I very, very often see stuff like that on cars that had major repairs like cylinder head or engine replacements and they don’t start after the repair. even more often actually, I see it on cars that had major work done within the past year because the wire harnesses are often not routed the same as before and they run along exhaust or sharp contact points.
@@SchrodingersBox Yup I often see problems from poor wire routing too, a lot of the problems I see are just as a result of laziness and carelessness such as not properly securing wiring or hack installs of aftermarket accessories. Just taking the extra few minutes to properly route and secure wiring harnesses goes a long way towards helping to ensure reliability!
Aftermarket accessories LOL!!! Oh man those are the best. I would estimate about half the electrical issues I see are from aftermarket accessories. And of those- probably 80% are for parasitic draws.
Good call. Heat and vibration first place to look
Another great diagnostic video. Yeah, I'll bet it was a whole lot of fun working in that tight space to fix the harness. If you are like me, when I have to do a repair in a tight space like that, you'd better tell the kids to play in the backyard or at a friend's house. I'll get it done after finding the issue, but the engineers who designed the car/truck will definitely be called some names not fit for kids' ears because of tight working spaces like that. LOL! Fortunately, my kids are grown now.
omg dude you don’t know the half of it... I was going to even do a video on it but I was so freaking pissed and out of control I just wanted to get it over with.
To drop the cat I had to remove the Y-pipe so I had to unbolt it from the opposite cat and to do that I had to a remove these stupid support brackets and of course everything was rusted so bad... then when I finally got that done the stupid transmission dipstick tube was in the way.... but the tube is integral with the transmission pan so I had to drop the pan to get the tube out of the way. Then when I finally got to the wiring it was so destroyed and brittle it kept breaking like pretzel sticks all the way to the harness so I had to dissect them out of the harness to repair them.
Then.... THEN I discovered the OTHER O2 sensor also had an open in its wiring so I did the whole job TWICE!!
I almost quit the channel at that point.
@@SchrodingersBox I feel your pain! I've been there more than a couple of times. I always say, "If I ever meet the engineer who designed this car, he will be spitting teeth after I punch him in the mouth!! and if he's a she, I'll punch her in the mouth!!" I think they should make engineers at these car manufacturers spend a couple of years working on these systems with a guy such as yourself so they can see what they design and how hit sometimes screws the person who has to repair it.
Hi sir,
Normally it's not a great idea to waste time on shortcircuit components just to show others you got the problem.
Once you show the melted wires it's OK.
AVOID going back to e heated up area/engine to fix the problem.
BTW...great and educational video!
Thanks.
👍😎
That thumbnail describes how I felt when I owned a 06 chysler 300
Nice video thanks for sharing. Those dang sensors I called it before even watching. Great deduction of reasoning and explanation on how to divide and conquer...Jay
Would a selection of plug-in circuit breakers be better than going through a handful of fuses each time you need to diagnose something like this? Or would they react too slowly to effectively protect the electronics?
EXACTLY! I know a lot of people use light bulbs and circuit breakers etc and actually I am sure they are fine however I absolutely worry about sustaining the amperage longer than what a fuse does and potential harm to the pcm or other components or even providing voltage to other wires in a damaged harness like this one (3 lengths of bare wire were all touching each other).
I am pretty sure, , especially on a 12V circuit, the light bulbs and CB techniques are OK but I just don’t like to take chances on something I might be unaware of and I almost always catch these things within 2 sacrificed fuses anyway.
@@SchrodingersBox Agreed on circuit breakers. Their slower trip increases blowing an ECM output if the problem is a shorted component.
Lamps automagically limit current which reduces the risk of blowing anything. And with this power>ground short you could connect the lamp from B+ to the circuit key off when all ECM outputs should be off.
And yes the battery is always spanked. Gas hand usually on E too. Unless it's the fuel pump................
Nice vid My approach is to confirm the customer complaint in this situation I also go to a wiring diagram which loads go to that fuse next is a visual inspection but never touch the wiring especially if it was an intermittent short to ground or another wire only then will I use a test light or bulb depending on if the pcm is in that circuit Just my 2 cents and by the way I’ve learned a lot from U Cheers
Excellent video. Very logical and sensible approach. Thank you!
I clicked the thumbs up button before playing the vid, I know Matt's gonna tackle this 😁
hahahaha. I appreciate it! it balances out those who click thumbs down before watching.... and they still watch the whole thing lol.
Great job I am one of you're do it your selfers with automotive experience . I like it when there is a Good short to ground on positive I put test light across fuse and when it lights bright short is there and when at half brightness has gone . Bulb now in series with load.
When your under the car the pitch makes you sound like bert from sesame street :3
hahahahah, i know it was trying to edit it out lol!
I soon as I read this I heard it 😄
Still got mad love for you tho guy :p
Thank u sir i really appreciate your knowledge 👍
Rather than sacrificing fuses and only getting one chance per fuse to see the fault, I use a test light plugged into the fuse terminal. Attach the test light to battery positive and then connect the tip to the leg of the fuse circuit that feeds the load. If it's shorted you'll get a light. Now you poke around the harnesses until you see your test light go out. In this case the light would still light through the heater when not shorted but once you find your suspect simply unplug the sensor and then use the light and poke around the harness. Though with other loads on the circuits this may not work every time.
Very nice video buddy. Can you show us next time how looks that burned whire or another component what you gonna have in the future pleas 🤗
Very good job - as usual. Enjoyed the process.
Thank you for sharing your work.
Thank you too!
Thank you, perfect and straight to point. God bless you always..
Another great SB video, really like the logic 👍
You don’t need a bigger garage, you need a shop building. 👍
Oh man I don’t want to do this full time lol.
My favorite thing is when a 60 year old mechanic tells me to "check 'the' ground, and clean it up".
I've literally had bosses tell me to "check the fuses" after I just checked a 10 amp circuit directly at the connector end with a 4.5amp test light and it was good.
Hi Zakee, 2003 Lexus ES300, Changed Battery,Alternator, then reconnected Battery, Fuse Blows, Turns Out it the Alternator Fuse, Replace Fuse, Reconnected Battery, Fuse Blows Again, Now Researching A Solution, Hopefully I’m not the Only Person to encounter this issue. Do you have any idea what I should Look For?
Sounds pretty simple- clearly a short. Isolate the circuit to find it without blowing fuse.
You the man bro. I'm glad to see you making videos again. You saved my azz a few times. ☺
Glad to hear it!
Re: you referencing your cramped garage- did you just give us a hint about something coming in the future?
Oh.... very perceptive. I can see where someone might interpret that!!!
If you take the blown fuse out and connect your test light across the fuse connections it will light up, if you then disconnect the suspect components the light will extinguish when the faulty circuit is found, it may save you a few fuses .
iiagnostics - a new word has been added to brain storage.
I really like your approach, thank you for sharing. Cheers.
Thanks for watching!
Tip.. Use the test light. Batteri + and the light on output on the fuse. Then unplug components until the light stop glow. Then you will avoid to use a lot of fuse
Thank you again I do have a question I want to learn more I’ve been learning with your videos but I want to get like a class online what do you recommend to do what classes you think I should take I had a class before online but then in the end they take it away you don’t get to keep the classes the videos or nothing when you’re going to go back you don’t remember something you’re done you don’t know anymore thank you and I was just wondering what classes online you recommend I only been working on cars for like four years I want to learn more thank you
unfortunately I don’t really have an answer to that since I never had any automotive training. I can’t speak to any classes or courses.
I had a 99 ford escord that was blowing the 20 amp fuse as soon as I would turn the key. I chased it down to the fuel pump module internally shorted, this module was located in the trunk left side of the firewall. Then I had other flushes blowing as well and bad alternator (would get hot by just plugging back the battery). I suspected a shorted regulator or internal component shorting out.
I would have the car off and connect the battery and the alternator would be hot to the touch after a few minutes. Main battery charging cable to the alternator was disconnected and it would get hot if the regulator was plugged so that's why I suspected the regulator activating something that wasn't supposed to, I think it may have been melted because this car had all sorts of electrical issues on the dash and even the blower motor that I have pending to verify if it is operational. I believe this was caused by someone who jump started the car with the polarities reversed. Melted a couple of things here and there. Including the pump regulator module.
Could you put a light bulb in place of the fuse? Then if the bulb shines bright, the short is still there. And you don't waste fuses.
I could but being a PCM controlled circuit I felt it safer to not keep in the shorted condition
@@SchrodingersBox , the headlight ( or smaller bulb) would limit the amount of current passing through the short.
yep totally agreed- I am sure it is safe but I also worry about the sustained current as opposed to a quick shut off from a fuse and what other circuits may be affected if the whole harness is melted like in this example. It’s probably ok especially on a 12V circuit but I am not much of a chance taker when I am unsure of the actual situation and I don’t like perpetuating the current through an unknown condition.
Thank you. Great Video. Thumbs Up
Grounds through coil in fords that year try replacing it in searry
you can use a plug in circuit breaker, saves fuses
This dude is good!
And funny And smart. 👍
Great diagnose Matt keep my friend. =)
Always!
Greetings Matt, I struggle to find free wiring diagrams can't afford as a DIY to subscribe to Mitchell where do you get yours great video by the way thanks man
I usually google them but I have started resorting to Mitchell DIY more frequently.
Thanks will definitely try it I appreciate you response
Excellent!
That was awsome well done 👌👌👌
Glad you enjoyed it.
That's amazing! U r my teacher!!!
dude get an endoscope with leds they be cheap now.
Good job man.
Hey tool man- where have you been???
Very busy but i was around youtube and i watch your latest video.
keep it up.
I definitely enjoy your videos
I'm so glad!
I have a 1991 nissan skyline and my fuel pump fuse keeps blowing. Where should I start looking?
It’s going to be Short on the fuel pump circuit.
I wonder if an alternative would be to use a multimeter on the fuse connection to measure the current, with settings that could handle the high load?
you can do that- or use a testlight
Do you ever use a test light from B+ to the fuse leg that's not straight from the battery to save fuses? Since it has a short to ground, it should light up until you find the problem. Maybe this would be a good situation to use an LED light, for protection purposes not knowing what could be going on with the melted harness stuff. I've have success, maybe luck, with the standard bulbs though. Last time I had a dead short like this, I used my power probe 4 in a similar way, watching the lights to change. I started by using the annoying beep sound, but it was too annoying.
yes that is a very good strategy indeed- I would have done that if I didn’t find the issue right away plus given the location of those harnesses it helped to see the spark
@@SchrodingersBox Yeah, whatever works! I like the isolation strategy. In a basic electrical class I went to, the instructor suggested using a bulb and PTC fuse in parallel while looking for the short. I haven't tried it, but some were skeptical of it responding fast enough while messing with the wires.
I NEED YOUR HELP. I have tried. 06 Acura TL runs fine cold, but stalls out at stop signs when hot. Cleaned throttle body only. Just bought spark plugs and fuel pump. Think it will help!!?
Wait I don’t understand- spark plugs AND a fuel pump? Is it an ignition issue or a fuel issue and how did you diagnose it? You totally lost me bruh.
Love your vids Matt! All Hail the Cat!
Get yourself a portable circuit breaker and jumper leads like Eric from South Main auto uses and that way you won’t go through multiple fuses while searching for the fault?
With all my respect let me recommend better way to find short to ground .Use Ohmmeter insted of fuse . IF second (not battery)pin of blowed fuse shows a few Ohms , then consequently unplug connectors till it will show more than 10 ohms.the latest connector is shorted to GND.
bulb across the fuse box terminals .. add a $20 inductive amp meter follow the current draw and you done in ten minutes
Yeah it actually doesn’t work that way on this circuit because it is not in series. On a parallel circuit you have to isolate the branches one at a time.
@@SchrodingersBox Ill start by saying in the spirit of you channel im only trying to help you and others reading this ... But Sir you are absolutely wrong if there is sufficient current flow to instantly blow a 30 amp fuse you have a permanent dead short ( it would not matter whether its in series or parallel but I cant think of any circuit on a modern car that would be protected by a 30 amp fuse and have component in series, id be interested if you could show me one as we all need to learn ) A bulb would limit the current flow, buy replacing the fuse with say a head light bulb then you would be looking for 4 amps (UK 55w) and a cheap dc inductive amp meter moved along the cables following the 4 amps ..... you are isolating the "branches" im sure you meant circuits by moving the amp jaws along the cables and noting the current displayed on the amp meter .... this can also be done with a compass moving it along the cables but takes more skill and care ....Like i say im only trying to help your views ..... and before you correct me i know my grammer and speeling is poor !! Best regard John
I'm seriously considering paying for your channels. So that I can be more competent or at least more experiences and with confidence.
you should do it! I promise you won’t be disappointed. if you are learning stuff here you will REALLY learn way more on that channel. it’s just $3 man- if you don’t like it, cancel. You won’t though! I get very very few cancels.
@@SchrodingersBox I will subscribe soon, after my busy schedules. 😊👍
My '98 LS400 had a crank no start issue....come to find out the sending unit appears to show the gas gauge much higher than it really is. I needed gas🙄🙄🙄
yeah that’s a good one! I had that happen to me too a while back. The trick to being efficient with that situation is being able to diagnose it’s a fuel delivery problem. once you confirm it’s a fuel problem you will pretty quickly narrow it down but even then it will be last on the triage normally because there is every reason the think there is gas in the tank. but for most other people that car is going to go through $1200 in parts first!
@@SchrodingersBox yeah at 1st I thought I didn't have my control feed on the fuel relay(this car has like 3 fuel related relays)🙄but that ended up being good. I knew it was fuel related but what threw me on a loop was the initial $5 of gas that I put in the tank wasn't enough....simply bc the gauge was damn near 1/4 tank so I didn't think it needed more gas. Two days later of pulling my hair out🥵I added more gas and viola🤣
Man that is some Jim Danner camera work under the car! ha!!
ROTFLMAO!!! hahahaaha. well hey I may film like him but you look like him lol!!!!
@@SchrodingersBox I'll take that as a compliment! HA!
Wire a 12volt light in place of fuse , unplug stuff until light goes out.
Great video !
Thanks for the feedback!
Why not just send a signal. And pick it up with a sensor?
I could do that but the problem is on a circuit like this the signal goes everywhere unless you unplug the components first.
i wish so badly you would do a p0300 random misfire on all cylinders...no check engine, with new plugs, wires and coils...perfect fuel pressure perfect compression, perfect o2 sensors and cat. bc i cannot for the life of me figure out what is going on
well you got new plugs wires and coils so I am assuming you have found it to be an ignition problem? If so what was the ignition issue?
You rock bro! Outstanding video and strategy! Only I can say: thank you!!!
Glad you enjoyed it!
Thanks again Matt and let me know how I can get to your pay Channel thank you And how I can pay you
it’s very easy. just go to www.schrodingersboxqm.com and you will easily be directed on how to access the videos.
What the causes of a P219A and P128B Air fuel imbalance? Fuel trim are good even at 2,500rpm any thought?
tons of things. too many to list. what data do you have?
@@SchrodingersBox codes P219 and P128B came out of nowhere car runs great Rpm drop slightly increase speed
No, I mean what are your fuel trims showing. what’s your MAF and MAP data? what’s your rail pressure?
@@SchrodingersBox I just notice my down stream o2 sensor read rich at 800rpm just checking that rn
Good
where do you get the wiring diagram?
I usually google it.
I have this same exact issue, how did you fix it?
Just fix the cause of the fuel trim anomaly.
@@SchrodingersBoxWould I be able to bring my 1995 Lexus SC400 to you so that you could fix this issue for me? I live in Los Angeles California
"Lieagnostics" I am going to use that one.
Disappointed you didn’t swap the fuse for a 55W bulb. When the light shines bright and short is present.
I could have done that but I can’t see the bulb from under the car. if I didn’t find the short quickly I would have set up my DVOM on a sound signal.
I liked the full beard better!
I believe you may be biased lol