Bad Engine Computer Testing Part 1
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- Опубліковано 16 жов 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.
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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 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 ua-cam.com/video/za13UnpbH7E/v-deo.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=
Great video. Long, detailed videos are always welcome. Anyone who says otherwise doesn’t have the patience to learn.
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 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 !
I'm being 100% honestly when I say you're the best teacher and best UA-cam 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
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
You are like the Dr. House of Auto Diagnostics.
Awesome step by step elimination of inputs and outputs
Thank you!
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
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
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
I wanted to just say you have done an excellent job, by far the best on UA-cam, totally in depth super detailed, ... wow keep up the hood work😮😮👍👍👍👍👍
These older videos are oldies but goodies always best to knoe your circuits everything else becomes easy to narrow Down @Scanner Danner
U just made understanding the electrical description in the back of my Haynes manual alot easier.👍🏾
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.
Thanks for videoing long scenes. It's awesome seeing a pro work.
This is way better than Forensic Files.
thank you!
Haha, so true! And that's saying something!
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.
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
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!
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!
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!!!
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!
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).
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 +.
you're the best teacher
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!
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.
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.
Well explained video, detailed informations, I proud to be on your channel
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.
This gentleman knows what he is doing.
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. 😁
Scanner Danner does it again..
Thankyou very much, for this good example of professional automotive electrical diagnosis. Very comprehensive.
+Volatile Motorworks thanks so much!
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!
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
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.
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
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
distributor,coil ,fuel pump, map,just about every thing anyone could think off has been changed even both computers
Injectors or regulator
Dan the man this Jamar one of your students from rosedale
Jamar! How are you? Nice to hear from you
Absolutely great case studies.....keeps me on top of the game. Cheers and keep em coming!!!!
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
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.
Excellent walk through and very informative. Keep the videos coming.
nothing is foolish by you. good work showing the ground feed to sensors at 40 minutes. Great detailing
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 UA-cam 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!
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 :-)
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!
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.
Great legend of diagnostics. Paul d.......
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
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.
Brilliant , great teaching skills . Well done
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
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
dude you are a great tech and teacher, have more confidence in yourself!
Thanks Jeremy
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.
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.
Great to see the gears turning and that you are human too....
I wish I found a fluke laying around lol great video
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)
When it comes to shorted reference circuits I swear it's always the last one you pull that ends up the problem 😒 🙄 🤣 @ScannerDanner
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
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!
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
Thanks a lot 🙏 Scanner Danner
Much support from 🇿🇦 ZAR- Durban
Rich Future by DSK Clothing ❤
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.
Bro excellent job of explaining everything with detail.... I couldn't like And subscribe fast enough!!
Thanks so much!
great lesson your diagnosis is excellent thank you
For an engine swap if you are hired to make sure the electronics don't get fried due to miswiring, I basically tell the mechanics not to connect the battery, in fact don't even install it. What I will do is charge the battery out of the car, and then power the car using a current limited DC power supply. For key off I like to set the current limit at 5 Amps at 12.5 VDC. Then I check the power feeds and fuses to see who has power. If there is a short because of the mechanics making a mistake the supply will current limit at 5 Amps which will not usually blow a fuse or damage a wiring harness.
Once I am satisfied the power and grounds follow the vehicle wiring diagram then I can go key on engine off at a current limit of 15 or 20 Amps at 12.5 VDC and see if I can communicate with the different modules in the vehicle; ECM, TCM, BCM etc. If so, then I will install a charged battery and continue my testing key on engine off. I always make sure the engine fluids are full before I start the engine. Then I will start the engine and look at ECM live data.
You really should not spark a plug when it is out of the engine, the excess energy not delivered to the gap will have to be dissipated in the driver IGBT which could overheat and fail.
I have always thought that the VREF should be a separate uC controlled supply within the ECM, so when shorted it would current limit and report a fault, whereby the uC could disable it. This way when you have a short on VREF the module can still function and convey the fault to the scan tool.
I can understand checking a few censors and if no voltage rise or drop, unplug the computer harness and start checking voltage pins coming out of the computer for proper reference voltages and if they are not present at the proper rate with a fully charges 12 volt system then make sure voltage to the computer is correct if it is the computer internal circuits are bad, open computer case as see what is burned up or start checking diodes if the computer was hooked up backwards due to improper ground positive contacts, should have blown the fuse-able link first inside the computer if not it will be diode that is blown. I would check diode voltage regulator circuits first that stabilize main reference voltages first. Replace and adjust parts to desired voltages ratings and proceed to next circuits, do the same and then run checks on the IC circuits to make sure not shorts or improper switching.
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.
Are there any free websites where you can pull up a wiring diagram to your make and model of car?
yes, here is the DIY version of the service info I use eautorepair.adtrk.biz/?a=10817&c=24&p=r&s1=
@@ScannerDanner Thank you for taking the time to respond to me Paul. I really appreciate it! More than you know. You're a great guy.
This is great stuff. Look how much easier it would be to put a new computer in at the customer's expense. I've seen lots of cars with £££££s worth of new components and a broken wire in the harness or an intermittent connection on a plug. As it happens you will need a new computer, but how much more satisfying and dignified it is to have gone through this step by step to eliminate doubt.
Maybe you could consider opening the computer and testing the regulator in situ to show how these things are constructed. It may be that a 2$ reg could fix this.
I thought the PCM components were soldered down. Are they serviceable?
@@scientist100 I'm not an expert on PCMs but as an electronics engineer soldered pcb items are replaceable as long as they can be identified and obtained. The knack is to identify the bad components and any underlying reasons for failure. Sometimes the components are ok but a soldered connection has failed due to heat stress or vibration.
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)
ua-cam.com/video/za13UnpbH7E/v-deo.html
ua-cam.com/video/uyncVz_HAtA/v-deo.html
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.
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.
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!
Even though there was reason to suspect the ECU, it still should be mentioned that the clutch pedal sensor is also an avenue for suspicion with a no crank in this car.
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!
u r awesome, I learn a ton watching u 30+ vids u speak your thoughts. thank u
+Robert West thanks man! only 570 more to go :)
Judging by what was in the video it may appear by hooking up the grounds to the starter terminal may have shorted out the ECM blowing the 5 volt regulator and losing the 5 volt power rail within the ECM. If the ECM has power at the ECM where it is supposed to have power and, now ground at the ECM, and you are still receiving 1.74 ref voltage, I would probably condemn the computer. I agree with Mitchel. Using a pinout diagram and using connectors from a kit, disconnect both harnesses from the ECM and connect power and ground to the pins on the ECM powering the ECM. Then check voltage ref at the pins on the EDM. With the harness disconnected if you get the 5 volt reference then you know there is a harness short, otherwise if you are still getting 1.7 volts then it is the ECM. Just a thought.
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.
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.
Hey Paul, thank you for all of the amazing videos, they’ve helped me tons! I have a question tho. So I have a 2010 Cobalt LT 2.2 automatic trans. It used to run excellent and everything worked perfectly. A few months ago I used HP Tuners to write a tune to my cobalt, now it won’t run, start or even crank, no click or anything. Everything else works except my fuel pump and starter. Starter cranks when I jump it @ relay but fuel pump won’t even prime. Lights, radio, etc. all work but my CEL doesn’t illuminate with all of the other dash lights. What all would cause my CEL to not illuminate upon cranking/starting?
the engine performance 2 teacher at my auto tech school shows your videos in his class just an fyi
Great video Paul!
Wow. I am going to name you AUTO DOCTOR🥰 GOOD NAME FOR YOUR BIZ💪🇺🇸💪🇺🇸💪🇺🇸💪
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
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.
How can any of your tutorials be TOO LONG. I can miss an important point if I take a sip of coffee. Your Video is like a TYSON fight. I sneezed, said "Gazuntite", and missed the whole thing.
Haha thank you Tom!
Fantastic video as always. This may seem trivial but could you tell me what test light you used ? Does it have to be LED or computer safe ?
mr scanner i think wrong diagnose for the getting 5 volt ref,you can use scan tools to check your 5 volts ref. if you check there is ignition and batt at your crank relay. so your next step check the ground ckt between pcm and crank relay.if ckt is ok, but still no ground feed from your pcm its means your pcm is faulty...sorry for my english
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
Hi I'm in Montreal Canada ... I guess I'll consider the online course, is
there an outline ? I've been working at a parts counter for 5 year, I am
not a "mechanic" Never the less I go around garages solving problems for
Mechanics in my area with the little knowledge I have .... Like yourself I
get a thrill when I get a car back up and running ! I have a good
understanding about relays, fuses resistance, diodes this is why I do well
but I need more ! I need to understand waveforms and O2 Sensors better,
also I understand that there is much more. I was watching your bad Engine
Computer Video and I was literally asking myself the questions as you were
trouble shooting and I could tell you we were in sync. It was late but I
couldn't fall asleep cause it was gripping ! Crazy Right ? I've seen other
courses and I fall asleep cause all I hear is about ISO standards etc
I love the hands on approach you do, again I will consider it.
Thanks,
Mike.
I totally call O'reilly's and have them send one of their counter hands when I have an issue troubleshooting. Never rely on my almost 20 years in the field, nope. Call the parts house. Where the professional parts people are that ask you if it's 2wd or 4wd when buying wipers.
I'm not sure what your point is ??.... O'reilly's is a parts store in your area?? Are you assuming all parts guys are the same? LOL
this guy is simply awesome. id love to have that kind of brain.
This brain barely passed high school and was a pothead for over 15 years :-)
i am refreshed with that 5 v ref voltages. something that I didn't do much.. thanks for the great video
thanks Glenn