Bad Engine Computer Testing Part 1
HTML-код
- Опубликовано: 18 дек 2024
- Here is the link to part 2 of 2 for this case study • Bad Engine Computer Te...
2008 Chevy Cobalt with a no start, no communication problem. Also no spark or injector pulse. I will walk you through the tests that I use to be as confident as possible when it comes to calling a bad computer.. It is not as simple as people make it out to be. Most people that replace a computer are doing so by guess work. There is no guess work in the processes I show in this video.
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.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdan... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.
Whoever comes across this video, it’s like hitting a gold mine.
Sir Scanner, Danner, you are the best teacher and I love you !!!
Thank you so much!
I have never seen diagnostics this deep. Seeing sensor getting tested out for pull down. I have never gone this far but your right there and it's practice. Lol
I Love real time diagnostics because it teaches the obstacles that we in the field may and will have to deal with to get it right. The thought process being narrated is awesome. I learn way better this way. It's real
Thank you! This is what I do on just about every case study I have. I turn the camera on before I even touch the car, so we can capture that real time diag.
Thanks for the comment!
@@ScannerDanneri attempted my own research on the ohm test you performed on the last 2 sensors and still am lacking in my understanding of: 1. What exactly is that reading telling us with regards to diagnostics - I understand an ohm measures resistance but if you are testing resistance between sensor positive and its ground shouldn’t it be basically approaching infinite unless it was on or shorted? And #2 which relates to my first question - how do you know what reading to expect/be comfortable with? Thanks for the educational videos - super helpful!!, I also find it easier to learn listening to your thought process etc…If you or anyone else cares to share your knowledge I’d greatly appreciate it - maybe explain like you would to a 5th grader lol😂
@@TheAbyssGazedBack First question to you. Why was I concerned about a shorted sensor? (this is why I was doing the resistance test between the 5v ref and ground circuits of all of those sensors instead of unplugging them)
Think about it. If you don't know, that is okay too! But it will help me guide you as to why I was doing these tests
@@ScannerDanner i really appreciate you taking the time to respond. Seriously where do you find time in the day? Apologies if the wording of my question was had to follow. I think we may have our wires crossed 😂. I just mentioned the part about doing my own research so I didn’t get 100 people responding that all the information is available and not try to take the easy way out..
I am asking because I find solving these ‘puzzles’ very interesting and I’m hoping you d help me understand. I’m currently attempting to diagnose a crank/no start on a ‘14 Audi a5 2.0t manual transmission.
Also do you or anyone who may be reading this know of a cheap way to get wiring diagrams?
Thanks again!
@@TheAbyssGazedBack this is my full time job these days 🙂
We had no 5v reference coming from this PCM and I wanted to make sure we didn't have a shorted sensor pulling it down. Like in this video ruclips.net/video/za13UnpbH7E/видео.html
And because some of the sensors were difficult to get to, to unplug, the resistance measurement at the PCM connector, between the 5v ref and sensor ground circuits answered that question for me! As far as resistance goes, I just didn't want to see something close to 0 ohms. Most potentiometers are in the 5k ohm range and you saw some of the psi sensors I think were in the 1.5k ohm range, which I found perfectly acceptable. Proving we didn't have a sensor shorting out the 5v ref circuit and condemning the PCM itself as the problem.
As for diagrams, I always suggest the DIY version of the same service info I use. It's like $20 per car eautorepair.adtrk.biz/?a=10817&c=24&p=r&s1=
Paul...Mr. Danner sir, you, hands down, deserve the "Teacher of the Year" award...no you deserve the very first "Teacher of the Millennium" award. Thank you for sharing. Thank you for caring. Just HUGE THANK YOU's for doing what you do for us! You're the MAN!!!
Thanks so much. Mean a lot
I much prefer these long troubleshooting videos instead of, say, a two minute video on how to fix a problem. You learn a lot more. Thanks.
I agree !
Scanner danner U saved me so much money by this video the same problem happened to my 06 honda civic coup sent to a shop and told me the ECM is blown so I conducted ur method and it showed me that it's giving me 5v I told the head Mechanic that my ecm is good he challenged me for that as I live in Beirut Lebanon here people r so stubborn and arrogant he placed a $200 bet with me and he will fix my car for free if I win so he lost bro I love watching and learning from u man
Great video. Long, detailed videos are always welcome. Anyone who says otherwise doesn’t have the patience to learn.
Awesome step by step elimination of inputs and outputs
Thank you!
I'm being 100% honestly when I say you're the best teacher and best RUclips channel for diagnosing these problems. You helped me diagnose on my car with what 3 different mechanic shops couldn't. Loving the long videos since you show your whole thought process and it helps us follow along and understand everything better
These older videos are oldies but goodies always best to knoe your circuits everything else becomes easy to narrow Down @Scanner Danner
You are like the Dr. House of Auto Diagnostics.
Good information even when missing the minor steps. Your mistakes teaches your students and viewers.. Over all I like this online video. You're very descriptive and thorough enough to the point one can understand the issue. Diagnosing is the most problematic and time consuming process
U just made understanding the electrical description in the back of my Haynes manual alot easier.👍🏾
I (many others) appreciate how you walk through you test procedures. There are other videos I watch to get my "quick fix" satisfaction. You could check vehicle first then video tape the results with no mistakes but because you are willing to make mistakes and share them with us all is quite humbling. Thank you brother !!!
P
Thanks for videoing long scenes. It's awesome seeing a pro work.
You are really good...wow. Spending an hour doing a complete diagnosis rather than simply hanging parts. I like your teaching style too...basically you were verbalizing your self talk. It works really well.
Thank you Jerod! My "self talk" is difficult sometimes. We definitely think faster than we talk and I miss things sometimes
This is way better than Forensic Files.
thank you!
Haha, so true! And that's saying something!
you're the best teacher
It's also important to note that when you put in a junk yard Motor and use that motors harness, it may have a different pin configuration even though the plugs are the same which will cause all sorts of problems. I've seen that a number of times. Good work though at showing what it takes to diagnose an electrical problem on a car. Most customers think there is a magic box that a tech uses that tells them exactly what the problem is. It's never that easy. Keep up the good work at educating people on how to find the source of problems cars tend to have these days.
Thanks Robert!
I wanted to just say you have done an excellent job, by far the best on RUclips, totally in depth super detailed, ... wow keep up the hood work😮😮👍👍👍👍👍
I like the way you are filming every thing is real and honest that make us learn more so keep it that way
many thanks to you
Thanks for noticing. Nothing staged here, it's all done live.
Hey Paul, I'm sure if I was working on this car I would be looking for sensors shorting out the 5V ref circuit too. But as I was watching, I realized that what we need to determine is whether the 5V ref circuit is shorted or if its just dead. So I had a "great" idea how to figure it out w/o disconnecting each suspect sensor. Use a low amp probe on each 5V wire at the pcm to see how much current is flowing on each 5V ref circuit. I don't know exactly how much it should be but I'm sure you could make a rough calculation by figuring the approximate resistance of all the sensors in the circuit. Also this might be were a similar car would help. You could take a quick current reading from it and then compare.
THANK YOU THANK YOU!!! The dealer quoted $1100 for my 05 Cobalt no start, no codes condition fix. Following your video, I began your diagnostics using my hands (LOL). Turned out to be a broken (S)terminal wire on the starter. $1.49 for 5 connector pack, some black tape, BANG she runs like a champ. Thanks for the $1098.51 bonus!!!!!!!!!
+77camaro unbelievable that you were told you needed a computer to fix a simple problem. These "parts changers" do horrible damage to my field. It actually makes me angry.
Nice job fixing your car my friend and thanks for watching
This gentleman knows what he is doing.
Dan...I have to applaud you in and for the video's that you do and the pro-diagnosing, etc.. I have watched a number of your video's over the years and have for the most part found them more so fascinating than educational.
Now i'm here for the education! I'm going through all these same stages as you do here. Well, I hope to complete these stages tomorrow Saturday as we are expected to have weather at or about the freezing point outside.
So to compound all of what you are doing but in sub-zero temperatures and on a GM Safari Van>>> Makes for an extremely difficult and frustrating experience to say the least. Thought it would be a simple thing but is turning out to be more than expected. Failure to locate and fix the issue this weekend of Feb 02 2019 during a tropical warm-up to 0c/32f, the vehicle will just have to go into the garage. I have been happy/proud to be able to conduct my own service/repairs "to a point", but in this case, I may have to succumb to defeat by mother nature!
Ok, it's after 10 pm Friday..... Time to sleep on it and watch part 2 in the morning.
Cheers
Oh...No i'm not a mechanic per-say. I have done a lot of mechanic services over the years on an as need basis. In my later teens, I took two years of mechanics schooling, serviced various marine and automotive engines. Things have changed slightly since then!
you are good at diagnosing. when i was watching it i paused it before you did the next step and we thought the same for the most part!
Great video as ever ScannerDanner Paul
I had a similar issue on a GM petrol engine. Instead of the control unit going down it was the split wiring supplying 5v to MAP and intake position sensor.. The wire had rubbed to ground pulling the voltage down.
I unplugged the control unit to eliminate then used a test light which would illuminate connected to Batt +.
Gentleman, u r good at this mechanical stuff! Respect.
Good education, swapping engine and all this work for a Cobalt seems over the top, though it was only 6 years old at the time, I wouldn't want to own this car though. It shows complex electrical ground problems probably are not for the person trying to fix their own car and require a wiring diagram and the confidence in reading it. What he could have done (though powering the computer without a harness could be tricky), is pull the single computer harness, power up the computer (connect all input voltage and ground), and check some (may one) output reference voltages on the connector. As a shop you want to work and there is no up side in buying a new computer, but as a fix it yourself and facing a $1000+ repair to do this, I would put $300-400 into a computer if I were not getting computer output from the diagnostic plug or (as in this case) getting these bad reference readings, and verified the computer had power (is your computer plugged in).
Dan the man this Jamar one of your students from rosedale
Jamar! How are you? Nice to hear from you
well you have a lot of patience i have experience in control wiring in havoc , comveyor systems etc , sometimes i play with cars not at the level you do , it can be a challenge for anyone you are good at it , i love watching you i guess when we get old i am 63 patience is a little short LOL . don't stop love your vids ,,,,
thanks so much!
Some friendly criticism.
When you hitting the car's paint with a metal testlight, you're penetrating the paint, exposing bare metal. Thats where rust gonna start forming, shortly after your repair.
Other than that, great video as always.
Scanner Danner does it again..
Thankyou very much, for this good example of professional automotive electrical diagnosis. Very comprehensive.
+Volatile Motorworks thanks so much!
You are a good teacher I know that's why you took your time to prove that was a bad computer that's what I was trying to say I wish I lived closer I Shirley would want to participate or just come and help you in my spare time to learn
I've been working on cars and such since a very young age and have seen the days of climbing in the engine compartment (literally) to adjust a carb to what we have today. Your videos are very thorough and in depth. I agree that you should not edit (for the most part) any videos. Sometimes what might seem insignificant at the moment becomes an ah hah moment down the road. Again awesome videos. Just subscribed and look forward to future videos.
Thank you Phil! You will not be disappointed. Between this channel and ScannerDanner Premium, I have close to 700 videos.
Paul, Thanks for this particular video. The very subject of "how to be as positive as possible that you have a bad PCM" is one I have wondered about for a long time.
I know you have touched on the subject in many other diagnostic videos. I'm looking forward to watching part 2, but this one has a lot of knowledge in it about how to "test pcm's".
It's a bummer that there is not a "universal PCM tester", that would have a bunch of different cables that would cover the PCM's in most cars, that a technician could simply plug a PCM into that would do a series of automated tests.
I assume that maybe some of the companies that do "PCM rebuilding" probably have test rig's like that, that they build themselves. It would not really be terribly hard to design, for an electronic engineer who had a good set of data on how the computer works.
Here is a suggestion for a video that I think would be of very great interst to many, many viewers, I know it would be for me....................
Please give consideration doing a video SOLELY on the concept of how many PCM's are replaced needlessly. I would be very interested in hearing, based on your lifetime of experience and other stories or data you have heard, is what percentage of PCM's that are replaced are actually OK?
I would bet the percentage is very high. I would also guess that in many. many cases the customer ends up paying for the garage to put the new one in. There are many ways for a shop to put a new computer in, then realize the new computer was not needed, fix something else that is smaller and cheaper, and get the customer to pay for the whole thing.
for sure, I'll have to share my experience with that with you guys sometime. great suggestion!
37:00 - "I have to get those other sensors out of the picture" Easy, unplug the computer, check resistance from the computer connector 5V terminals to both battery positive and battery ground. as long as you don't see a low reading, you know all the sensors on the circuit are good. No need to do all of the physical leg work unplugging sensors.
Right one, that is where I went right off.
Great legend of diagnostics. Paul d.......
ok ty for beating this into my brain.. low ref voltage on entire circuit. check main power unplug or ohm check sensors. no short in circuit. ref low to gnd.. for resistance check. got it. this means sensor has resistance so sensor is good and wire integrity is good. bad ground will give us high ref voltage. thanks again🤩 on to part 2 now. understand your circuits and fundamentals!!
Thank you! You will enjoy the part 2 video as well.
Another great video. Man I’m learning lots 👍
You are watching the perfect set of videos for your issue!
@@ScannerDanner Great. The cold front has lifted. Just have to clean the Snow off and get back at her. Can’t wait. I’m excited. Even though it’s just my Farm truck I wanna get this problem corrected. 😁
Well explained video, detailed informations, I proud to be on your channel
Great work, my Idea was to, disconnect the ECU connectors>>no 1.7V>> use an external 5V PS with a current gauge>> inject 5V to check short circuits on the entire 5V Ref>> if no short present and 5V was up then we have a definite bad ECU
Hi Paul, love the tutorials. I've decided to get back into diagnostics having been out of it for a few years on the strength of these (perhaps you just make it look too easy)!
When testing for possible shorts to ground of the 5V ref. circuits, how about just doing a resistive test at the ECM plug (plugged in - possibly battery +ve disconnected so no stray voltages) on each 5V ref. connection, and probably eliminate shorts with a couple of measurements? You'd be getting a number of sensors in parallel but as long as you don't see any readings less than, say, 100s of ohms, those circuits aren't incorrectly loaded!
Can't wait for part 2!!!
I haven't watched the whole video yet, but, knowing the wire colors were wrong at the throttle body and that this is now the second engine installed from a salvage yard I would suspect that the tech that installed the engine kept the engine harness intact with the engine and that it may have come from a sister car that shared the same engine. i.e. I would move my testing to the ECU connector and confirm with volt drop tests across the circuits to connector end views. This has saved me in-numerous hours of frustration with budget mechanic swap diagnosis once I figured it out. Just thought I would share.
while you are checking the 5-volt reference move the wiring harness around and wiggle here and there to see if the voltage comes back up. Seams as it is the ECM. Due to engine replacement, id check for a pinched harness spot maybe during the engine install. I think you're pretty talented at this. Sometimes you can open up the ECU and see blown components or hot spots or swollen capacitors or swollen female connectors not supplying enough voltage. The wiggle test helps here while looking at the voltage meter. ( harness connectors ) You covered all the basics pretty quick a color-coded wiring printout would be good here
Cool. Without wanting to draw you or anyone else into an argument on this topic, I just want to say that, in my opinion it doesn't matter how experienced a person might be, to bad mouth a peer is just bad form. After all as the saying goes there is more than one way to skin a cat. Your videos are excellent BTW.
What you went through in this video it was amazing step by step analysis from the schematics we have to use schematics in our channels however if there's a place to open up the fuse to the computer I would take an external power supply at 5 volts with high current feed it to the computer to see how the computer reacts and see how much current I am drawing
nothing is foolish by you. good work showing the ground feed to sensors at 40 minutes. Great detailing
Would it be wise to just cut the 5v ref wire at the computer and measure voltage there to determine if you have a wire/sensor short? Or would the splice cause problems? For the sensors that you can't get to.
Wow ! I am a beginner. I learned a tremendous amount ! Thank you very much. I actually will need to watch this video again ! Thank You Scanner Danner !
Glad it was helpful! I have hundreds and hundreds more :-)
Hello I watched your video and I was like watching a great drama movie! I love the way you troubleshoot like I said it was gripping I followed you right through while I was asking myself the questions you were answering them amazing wish I could come down to that school and learn something with you ! Great job !!!
+Mike Nitti thanks so much Mike! Why can't you come to RTC? Would you like some more info about our school?
Either way, you can follow me here on RUclips too! I have another channel that will bring you into my classroom for $10 per month. It is the next best thing to coming in person.
Let me know. Thanks again!
Have you ever used a power probe hook on a 5volt ref problem?
So if you set the hook to 5 volts and tap into the circuit, it beeps if the circuit or sensors are pulled to ground. Then you can unplug one at a time and the beep goes away and probe shows 5volts. Bam, short found!
I don’t know how I got here but I’m enjoying it 😂
Glad you're here!
Absolutely great case studies.....keeps me on top of the game. Cheers and keep em coming!!!!
@18:20 maybe I need to get out more but I have never seen an injection moulded clutch pedal before. That worries me because failure of that part is seriously dangerous.
distributor,coil ,fuel pump, map,just about every thing anyone could think off has been changed even both computers
Injectors or regulator
Very good video it's always a pleasure watching your videos, as they remind us how not to forget the steps and follow your book, tank you ,and please keep this good job that u always do.
Have 2000 Ford Windstar and need to replace computer myself. I did find the PCM but don't know how to remove it. Do I need special tool? Do I remove through engine side or glove box side? Where would I find the number? Thank you. By the way, I enjoy your videos.
Good video. It's also good to know to stay away from the Cobalt
I have had my 2008 Chevy Colbalt for 12 years and it has been the best car I have ever owned. Has 150,000 miles and still purring. Basic upkeep like any car.
I'm in this thread after my 2006 2.2 gave me 11 years and 199,000. If I can figure out the gremlin someone else can have the last few years... But still made it that long. Not all of them are lemons
Brilliant , great teaching skills . Well done
Is the 5 volt reference signal from a known position on each sensor? To determine whether input is good or is computer just looking for any signal on return line to verify communication between the two? I am presuming this is for verifying a signal is present before start up. Also are there any internal fuses on vehicle computer to prevent damage? They don't go bad often but like you have mentioned they aren't interchangeable or cheap either. Thanks for the videos.
Please explain what you meant by, "...a bad ground would give a high ref voltage." Thanks for your great vids.
I think bad ground wiering from air space or corrosion ,causing current to flow pourly on cars negative side , leaving batterie positive side higher voltage cause the volts arnt making it through the negative
Hey Paul nice video I have a question is that procedure the same for all the veichles that have that kind of problem that don't want to start. To check grounds and powers of the computer and then check the 5v refrence on the conectors. Thats my question. Hopefully I can hear from u. Thanks scanner danner.
Excellent walk through and very informative. Keep the videos coming.
dude you are a great tech and teacher, have more confidence in yourself!
Thanks Jeremy
Working on the same car with similar readings...the highest readings on any sensor is .06 but when I unplug the bottom ecm connector the readings jump up to 3.3volts don't know if that tells me anything or not... ???? going to check the fuel pressure sender like yyou suggest and call it.... I recently signed up for your class.. you have made me lots of money and the lest I could do..so thank you and keep on keeping on. :)
Thanks so much! Follow my Chapter 9 playlist for more on testing the 5v reference circuit.
Of course I'm referring to a power supply that's variable that you can put in 5 volts 12 volts try to feed it at the fuse otherwise chasing all the loads that are connected to it is a lot of work
Scanner Danner help? We bought a 2007 Saturn ION. Has a misfire on #4 cylinder. We swapped nogstics everything. Did compression test and #4 has 170. Did continuity on all the wires on#4 and no breaks.
Paul I have seen the wiring harness rubbed threw both the crank sensor and coolant temp sensor three times on this engine where the harness wraps around and down by the oil filter metal housing on the block. Hope this might help.
Brad
Thanks Brad. The car is fixed. Part 2 is complete. Hopefully that tip will help in the future.
Danner, I had a case two days ago with a computer ground not fully grounded to chassis. The voltage I was seeing at the sensor ground from computer was 5 volts (as if it was a reference voltage). I was puzzled why I was seeing 5 volts on the ground with key on engine off. I was expecting to see zero volts but I was seeing exactly 5 and that was consistent for all sensor grounds that were shared from the PCM. Resistance from battery post was 0.1 ohms, with plug disconnected from PCM (isolated). I also unbolted the ground where it was connected to the car frame and had about 6 pins that were spliced somewhere and fed into the PCM. I did a voltage drop test measurement while the PCM was connected and I could see noice but voltage was near zero. I would touch a good ground and the line would almost flat out, the noise I was seeing from the computer I thought were from sensors deaeing little current etc but I was still suspecting a bad ground. Like I mentioned before, when I removed the bolted ground, the wiring and bolt looked clean, little smudges on it because if being old etc but I cleaned it anyway just for kicks and after that, all issues were gone.
The car would start, throw me all kind of codes, including the ECT, MAP, CAM sensors, engine oil temp, transmission pressure line with the thing in common of High circuit and at some point low circuit (based on the type of current the computer needed to see).
Symptom was a long crank before start and no acceleration (ECT was dead). This was a 2014 Dodge caravan that was in an accident that damaged the PCM, replaced ECM and dealer suggested then to replace the wiring as the plugs were damaged, reprogrammed the PCM as the owner had told me that it started only once with no acceleration but then it would not start, it started for me but like I explained.
The key point here is that i did a drop voltage test on the ground and when unplugged, it looked perfect, when plugged and ignition on, I could see noise and I attacked the ground. The thing was that the ground did not look bad at all and could have fooled anyone, in this case the ground had some sort of resistance which would not send them out from the PCM. After I cleaned and bolted everything back together. I took a measurement at the sensor grounds and the voltage was perfect zero and no noise or 5 volt as the initial reading. Would it be safe to say that the ref signal was being passed through one of the sensor if it were to be unplugged from the PCM or the PCM sending that bad signal intentionally because the ground was not gold enough? Unfortunately I dont remember testing that pin out from the wire unplugged, if I recall correctly I think it was outputting 5v because the other plug was still on so I think the computer was defaulting to 5 volts as bias when no ground was present. This was a huge experience for me.
Reference voltage signal was good by the way.
Excellent video. The logical path to testing all of this sensor stuff is just like what we folks who used to be consumer electronic techs learned about VCR's in the mid-late 80's (you remember VCR's, right? (No, that's not the one with a crank on the side!). They had mechanism position sensors (sort of like a throttle position sensor), & Hall motion sensors on the VCR mechanisms as well as signals from the tape to keep it tracking & of course the processors that used all this info to make the thing work. it was all completely new to us back then.
I will say that the reading on your Fluke for the reference voltage is actually 0.174V and not 1.74. This could easily just be the wiring harness acting like an antenna & picking up any errant signal in the air. It could also be the result of the computer being bad, too.
Ultimately as you said, it's basically no voltage compared to the 5VDC that should be there.
Great video. I'm really just your curbside mechanic who has an electronics education, and really see the parallels to the consumer repair electronics industry which has unfortunately been essentially dead for quite a few years once that kind of stuff started becoming throw-away. That is a distinct advantage the auto industry has. Vehicles have not gotten cheaper to replace, unless you bought a Yugo!
Glen Whatley I'm 75 started w bw. TV's 1950s retired 2007 watch theese videos realise a modern car you haven't got a chance even with the dealership this guy needs equipment diagrams & a second sense detective which you develop a experience elect .techs once could make decent living in the day without getting dirty.
You are truly amazing! I've spent hours and hours watching your videos on no start no crank situations. Loved the one with your son! But I have a Dodge Stratus that will not start or crank and we can't figure out what we should do next. We replaced the starter and ignition switch, which, after watching your videos, I now believe were a waste of money. I've tested the ignition switch for power when cranking and all is good. I've tested the starter relay and it has power on the load side and on the control side when cranking. But when I tested the brown wire that attaches to the Starter solenoid and sends power from the ignition switch, there is no power. I just don't know what is in between the relay and the solenoid because I can't seem to find a wiring diagram for my 2.7L sedan anywhere. I'm not sure if the Neutral Safety switch is involved in the circuit or if its just the PCM. I'm afraid it is the PCM though because the odometer is reading "No Bus" and when I turn the key to crank, nothing happens. No spark, no crank, and no fuel pump priming. Do you have any suggestions on what I should do next?
+Christy Frye I do and the "no bus" message is where we need to start. Unplug the throttle position sensor or map sensor and see if you have 5v available to either sensor.
Watch this video and you'll have an idea of what I'm talking about.
(shorted crank sensors are known to pull the reference circuit down and cause you issues but don't go run out and buy one just yet, do those voltage measurements)
ruclips.net/video/za13UnpbH7E/видео.html
ruclips.net/video/uyncVz_HAtA/видео.html
Keep doing your thing brother. Just saw the FB post and it made me see red. Ignore the stupid people man. You are a good man.
Would the ignition control module be getting 12 volts if the computer is bad?
I think it depends, if there’s power from battery to ignition then to computer
thank you for the video youtube. i am working on a1990 thruderbirt 3.8, i think, supercharged no start and 3 bad capacitors. replaced the capaciors, but still no start and seems like no communication with the engine eec. will start with exactly what you showed in this youtube. but have no wiring diagrams yet. thanks again. edwinstarr24. this video is very helpful. ed.
Service info help. This is the DIY version of the same service info I use.
eautorepair.adtrk.biz/?a=10817&c=24&p=r&s1=
With your key on, do you have a 5v ref on your TPS or MAP (if you have a MAP)
Using a resistance check at the PCM to verify that sensors that are a pain in the ass to get to and unplug ain't shorted to ground. That's an excellent idea!!!!
Yea, in this case that was definitely the ticket. In other applications, where the computer is buried and the connectors are some difficult to get to, this may not be the method to use
great lesson your diagnosis is excellent thank you
Nice work again brother,,so your saying that a high voltage on an egr sensor per say,, with a working computer given a code of higher voltage value than normal would be a ground issue on that sensor circuit?
Great to see the gears turning and that you are human too....
I had to go through d same process a few weeks ago, and found d 2002 Saturn Vue needed a computer, which fixed d problem. So I know what you r going through.
Very nice video ,helpfull!congratulations Mr Danner,keep going!one question,what type of the Fluke you are using?
not sure, it wasn't mine, sorry
Thank you very much for your video. I have a question though. How to determine whether the problem comes from the ECU or the wiring harness? I am encountering problems with my Ford Probe GT and I need an answer...
my respect for you lol the video and seen tours are excellent a good teacher l also works mecanico automotriz and still everything learning in nicaragua but live in California speak little English but when it comes to the mecanico automotriz understand perfect well my respect for you master
+Noel Matute thanks so much Noel!
Around 39:55 you said that since the clutch pedal position sensor signal and ground wires go to the computer, it could be shorted and you might not be able to see it? if the meter reads OL, doesn't that mean there's no continuity between the battery negative and a potential short to ground?
just watched your expanded content video on your premium channel and realized you were checking for a shorted sensor LOL but I still dont understand the statement you made in the video.
Which statement Michael? Sorry
Around 39:55 , "The clutch pedal position sensor and ground wires all go in this(PCM) too, so it could be shorted and I'm not going to see it" . then what you did was just switch your meter ground from battery ground to sensor ground.
Yes, with the computer unplugged, if a sensor ground wire was shorted to a 5v ref wire and I'm measuring the 5v ref wire compared to battery ground I am absolutely going to not see that condition. This is why I moved my meter ground to sensor ground. So there were two different tests for a short to ground on the reference circuit. Make sense?
Yes makes so much sense now, haha I feel kinda stupid. One more question though. Everything you did in this video is because you're worried about a shorted 5v ref whether it was a shorted sensor or harness, but wouldn't that cause the 5v ref to be pulled all the way down to 0v like the Cadillac DTS that had a short to ground in the harness somewhere? or is still possible, like a partial short?
Thank you so much for responding to my questions! It's summer here in Canada but here I am watching your videos and learning. I'll be going back to school this September and we'll be doing diagnostic work and I'm pretty sure that I can apply everything that I've learned from you.
paul I would love to geton the shop one of those bad pcm like that to test coils, will be nice to have it
Great video Paul!
I was going to ask you if you could put a 5-volt reference on one of the components and then you mentioned it on the equipment I work on some of the 24 volt systems use a 8 volt reference I have learned a lot watching your videos I would love to have your book everything you teach applies to everything even heavy equipment
so much of what I cover applies to everything! Even beyond cars and trucks. Thank you so much for this comment. This was a good case study. Have you seen part 2 yet?
Yeah I seen part 2 that was pretty cool the crank sensor not plugged up
When u were checking ohms on the sensers , could u have checked voltage to see if it dropped for current flow ??
+marianatequiero28 not sure what you mean. Could I have tested for excessive current?
Paul when you get a no-com do you do a voltage drop on pins # 4&5 of the data link connector looking for voltage on the chassis & ECM ground ? Or do you just look for the 5v at the engine. Look forward to part two. Great stuff. Thanks
Depends on the symptom. In this case, I never worried about the data bus network being the issue. Easier to verify 5v ref first.
No easy answer there Steve. No coms suck! Mostly because they are intermittent and are usually functional when they get to me.
Also, to be honest, most no coms I see the problem is NOT the network. Ignition switch here, blown fuse there, shorted reference circuit, water in the fuse box, water in the air bag module under the passenger seat, a piece of metal in a bulk head connector shorting the network to 12v.
An frozen LF caliper with U codes all over the place. Fixed the caliper, the communication issues disappeared!...sigh
Steve, I was just talking to Paul a few minutes ago, and he said that there is several 5 volt REF wires coming from individual sensors going back to the PCM separately, but they all connect internally. I still believe that we need to confirm that the 5 volt Refs are not shorted and dead, before condemning the PCM. We need to find a quick and easy way to isolate those Refs from the PCMs. If there was a way I'm sure he figured it out! I believe he posted to someone that the car is fixed . We need to Brain Storm to try and figure this thing out before he posts the vid. You Game!
What I notice is pin 4&5 on a no com that has the 5 v ref shorted to ground will show up as excess voltage. Another variable may not be repeatable on all systems.
ScannerDanner Paul could there be another module that uses the 5 volt ref on that car that is pulling it to ground?
Billy R hey Billy sorry to leave so fast last time but that big feed of trout was shall I say a little on the greasy side HA HA. Cant argue with Paul he's bang on with all the refs are joined internally. Not sure if I could be much help plus brainstormmin wow how am I going to get up in the morning to go moose hunting.
Any corrosion on the terminals on the plug and computer terminals that electrical spray cleaner can fix? You might have checked that but thought I'd mention it.
Hi great video to prove the computer is possibly giving out low 5v sensor voltages would it have been possible to back out the sensor feed wires from the connector this would take any loads of the circuits,. this would then give a true voltage output from the computer,kind regards Mike
+Michael Stanley The main purpose of the wiring harness is to securely and reliably convey different voltages, grounds, signals, etc throughout the vehicle. Many connectors are permanently assembled unto the wires and in only limited cases can be disassembled without damaging the connector. you normally have to disconnect the connector and test the wires separately within the plastic enclosure or test while the connector is still connected.
Danner thanks so much for you video your personality ! approach ! techniques !
are second to none !!!!!! absolutely the best i have seen you have given me insight and pleasure to delve further than i thought were my limitations ! with great enthusiasm
with your video,s to back up i feel confident god bless you and your family regards steve england
Thanks Steve! Merry Christmas
ScannerDanner hi Sir thank you for this video ... one question where do you get this electric diagrams from??? Thank you in advance
eautorepair.adtrk.biz/?a=10817&c=24&p=r&s1=
Hi Paul - fantastic - just amazed at the thought process, lots of variables in diagnostics. I am so glad it's not an iac. LOL
Haha I know right
lol hey! IACs wouldn't be so hard if freeze frame and scantools didn't both conspire to tell the same lie!
Schrodingers Box Still having iac nightmares Matt. Feeling a whole lot better into the future knowing our overlord is looking over our shoulder to keep us on the straight and narrow. Schrodingers mail box without an P.O. box as well, what about the guys without a computer, never though of that one A. Caught a 4 pound trout yesterday , could send you one. LOL Pax vobis.
Schrodingers Box Matt, It's over, We Hope! Stop crying!
I know it! Back in the day the Snap-on scanners had a glitch with upstream O2 s on Nissan. The OEM mode even gave the wrong trouble code! The global mode had it right....nightmare when those things happen. I certainly can relate my friend. But hey, look at it this way, you'll always have that one thought it your head now "is the scan tool lying to me?" It's a good question to ask yourself.
Awesome video! Can you put a video of computers that need programing? After replacing!!
+luis freitas I have one on a Volvo on my premium channel. Would you like a coupon for a free month? email me through my website and mention this post
When backprobing the reference and ground on the computer harness could you fry the driver if those two T pins were to touch?
Good question. There is no "driver" for the reference circuit like you would have for output controls. The ECM has an internal 5v regulator that is pretty well protected from shorts. It wouldn't be a good thing to do that though because you'd pull the reference circuit to ground. It would recover when you take the short away
@@ScannerDanner Awesome, good to know. I bought your book and have been following along with corresponding videos. I'm amazed at how fast my mind is absorbing your methodical/ repeatable approach to diagnostics, and am on the cusp of subscribing to your premium channel knowing that your classroom lectures will have tons of these same questions from your students. Absolutely top notch Sir, many thanks!
Thank you so much!
Hello! Was hoping to get some helpful information from you regarding our 2020 jeep cherokee. It all started about a month ago when I noticed after starting my car that all my preset radio stations had reset itself back to factory and unpaired our cell phones from the Bluetooth. I thought kinda weird and a week or so later I got a battery notification on my dash for a split second but than it went away and didn't happen again. A month later the check engine light comes on. Our car has 95k miles and we are the second owners. We bought it with 85k miles from our local Lithia dealership. A handfull of times the e brake would set itself sometimes when i was backing up even and a few times when sitting in idle. It was starting and running fine other than those issues up untill yesterday i turned off our car and 5 min later went to start it and nothing. It wont turn over. We tried to jump it- nothing. Tried putting key fob up to ignition and nothing. Checked all the fuses- no blown fuses. Checked ground cables, connections that we could see to make sure they are good and seem to be.The e brake light has been flashing also and the brake set itself when it wouldn't start and I can't get the ebrake to unset. Its pulling a U0100 code. If u gave any info tnat might help us or any ideas please lemme know. We would be forever grateful. Thank you
I love watching this channel and having it as a reference. Where is Scanner's shop located? I wish he could help me figure a p0765 p0768 "shift solenoid d" electrical fault. The funny thing is, the solenoids aren't changeable, you have to change the whole pack, 6F50 Ford. This is the second allegedly new one I've tried, both, display different issues. One wouldn't recognize the TSS sensor, now this one says shift solenoid d issue. I'm using FORscan to try and figure it out. The shift solenoid d light didn't come on until I had shifted gears in place for a while. Everything was really smooth at first, then after shifting N,R,N,D,R,D,N with at least 4-second poses in between, it eventually pops the codes. Maybe the fluid is contaminated somehow, even though not old. Thanks for your awesome videos, Scanner Danner!
nice video. can you unplug the computer and ohm test the remaining wires the way you did your hard to reach sensors for a possible short to ground or test light to positive test the signals to load them a little?
Yes. That is exactly what I need to do. But I'm not concerned with the signal wires. The ohm test gets done between the 5v ref wire and the sensor ground wire to test the sensor for a short. Then from the 5v ref to body ground to test for a ref. wire short to ground.
Paul, I just got done watching the vid, again and I still love the way you checked the hard to reach sensor wires. After watching the vid again, it left me with three questions. My take on it was that when you did those ohm checks that you were proving the 5 Volt Ref was not being fully pulled to Sensor Ground thru a shorted Sensor, by having about 5,000 ohms of resistance. My question is by doing that type of test are you proving ( I don't believe you are ) that there is not a Short to Ground on that Sensors 5 Volt Ref to Chassis ground? Did you mean afterword's that you needed to check that there was not 5 Volt Ref Short to Chassis Ground when you said we might have a Harness problem? And if the PCM is dead, then why is there that 1.75 Voltage still on the 5 Volt Ref ? I watched your Honda Element Vid and you had a shorted MAP Sensor that was pulling the 5 Volt REF to Sensor Ground and you had that same 1.75 Voltage on the 5 Volt Ref? ( Clue ) - That common denominator between the two case studies needs to be investigated. That exact voltage 1.75 on both vehicles cannot be coincidence ). One other thing that tells me that the Regulator is still good, is that most Commercially bought Regulators ( not sure about the PCMs Regulator, I would think they do! ) have a Thermal/Overload Shut Down feature built in internally to them, which makes them almost impossible to cook. Also there is a thing called Dropout Voltage ( Usually 1 -2 Volts higher than the Regulators Output ) on those Regulators. If the PCMs Supply Voltage drops lower than the Regulators Dropout Voltage than the Output Voltage on the Regulator drops accordingly. Another words if your Supply Voltage had a Voltage Drop because of Resistance or was pulled down to ground but not all the way, the Output on the Voltage Regulator would Drop too! My prediction is you found a Shorted Sensor or Pinched Harness somewhere or a Bad Power Source to the PCM. You fixed It so I guess well find out soon!
1. I was proving the sensors were not shorted only.
2. A short to ground test would need to be done next. It would involve one test lead going to body ground and the other to each ref. wire with PCM unplugged. (this test has not been done yet)
3. The 1.75v is a coincidence (I promise)
I knew you were aware that more testing had to be done to confirm no shorts to chassis ground, I just wanted to confirm that for my own thinking! It's like a game of chess, it's all about strategy! And about 5 Volt reference being 1.75 Volts in both Case Studies not being related. Still think it is worthy of study to see what actually cause it to read 1.75 Volts, forgive me but I have a little of that Conspiracy Theories in me! LOL! I guess I will just have to wait till you upload Part 2 to see what the fix was! Hurry Up Please!