Hey all, I hope I’m posting this is the right place to find the most knowledgeable people to help. Here’s the deal: I have the following current codes along with “service engine soon” on the DIC, and check engine, traction control, and ABS light illuminated:

2002 Base C5 coupe, manual trans, Auto climate control.

In 10-PCM: P1571 ASR Desired Torque, and P1689 ???? (Can’t find this code description anywhere)

in 40-BCM: B0432 Rear Defogger relay circuit

In 58-SDM: U1040 Loss of communication with TCS


Here are the recent related events I’ve noticed:

I’ve noticed that the analog voltage gauge needle on the dash seems to take a while to reach proper voltage upon startup. (The digital readout in the DIC reads proper voltage) As the needle is coming up, I get all the warnings and lights in the systems mentioned above. Almost as though they’re not getting the power needed to “pass all their tests“ upon startup.

I’ve noticed more recently that when the warning lights are all on, the HVAC system (its an Auto HVAC, not manual system) will not work.

Sometimes if I start the car and get all the warnings, I can turn it off, immediately restart it, and everything will reset and be fine.

One time, when the warning lights were on, and the HVAC was not working, I tested the systems by braking hard (ABS did not function and I locked it up) and accelerating hard (traction control and ASR did not function and spun the tires) and confirmed that, as designed, these systems were off when the warning lights were on. Funny thing was, right after I did that (about a minute), suddenly the warning lights went off, and my HVAC system immediately came back to life, and all systems functioned properly. Then everything was 100% fine the rest of my drive until the next day when I started the car again.



Things to note that may be related:

I’ve had the alternator rebuilt. It is the original one still.

I recently (a few months ago) sent out my EBCM to ABS Fixer to have it rebuilt, and it’s been fine. These problems are similar to why I had it rebuilt, but not the same. That was the common C1214 error code, and that hasn’t come back.

There is a relatively recent new battery in the car as well. I replaced that when I rebuilt the alternator.

I drive the car almost every day, so it does not sit long enough to discharge the battery from not being used.



As listed above, I know what the code descriptions are except for P1689. I wasn’t able to find the description for that one. Anyone know?

So has anyone ever seen this combination of codes? I find it very strange and can’t figure out the common factor between them all. I’m thinking maybe the alternator needs to be done again? It seems like some sort of loss of power, but that’s just a guess.

I am a pretty decent home garage mechanic, I’m not afraid to take things apart, and I try to learn and gather as much information as possible. But I am not a professional mechanic and there are many things that are over my pay grade. Electronics are not my forte and when it comes to circuit testing and such things I’m not the best. But I can definitely take out and replace an alternator, water pump, ebcm, valve seals, suspension parts, etc. That kind of stuff I can do. So I’m hoping someone can lead me in a direction which leads to a fix I’m able to do myself. We will see.


Thank you to anyone who has read to this point and is willing to help!!! I look forward to any responses. Thanks again!

 

Also, I should add that when running the codes in the DIC in the 28-TCS and 99-HVAC modules it showed NO COMM. I do not know if maybe it should be communicating with those modules and perhaps the fact that it’s not is indicative of part of the issue...?

Thanks again to anyone who may be able to help figure this out.

 

I see no answers for this one and I am experiencing the same in my 2001 Base Model with 17,500miles. Picked up 2 years ago and problem free up until now. Hoping a bump might get an answer as my inspection is due this month. First I cleared all of the codes it had and then went through them again. These are the codes:

SDM-U1040 H C, BCM- B0432 H C, PCM- P1571 HC and P1689 HC.

I also have the service vehicle soon message, traction control and ABS lights on. When the ABS light is on the AC does not work at all. The problem has been intermittent for the past couple of weeks, but now is pretty consistent. It was not a problem yesterday, but today, there it is again. Please help. I wanna drive the thing like all vette owners do.

 

I was surprised to see someone reply to this thread that I had posted in Sept of 2020, because nobody ever did back then. I hope I can help you out here because I think I remember how I ultimately solved those issues. Although I forget where I found it now cause it was 5 years ago, I remember reading somewhere about cleaning the key ignition cylinder. I removed the center console and removed all the trim panels I had to so that I could access and remove the ignition cylinder. There are a number of small electrical contact tabs in there that all make contact with either the key or the cylinder when you turn the key to ON (I forget which cause it’s been a while). When this contact is made it sends electrical signals to multiple computer systems in the car “telling” them to run checks and basically initialize their systems. These contact tabs tend to corrode and oxidize over time, and so when they make contact, the strength of those signals is weaker, and essentially all of those systems which are expecting a certain voltage don’t get the signal with full power, and therefore “think” there are errors and start throwing trouble codes and causing certain systems to go into fault mode and not work. (Such as was the case with my HVAC, ABS, etc). Once I gained access to those little tabs (copper I think?) I carefully cleaned them with a small brush and electrical cleaner. I was easily able to see how dirty they were, and the clear difference once I cleaned them. I put everything back together and started it up, and never again had a single one of those issues. It’s been almost 5 years now and those issues have never come back. I’ll try to see if I can find a link to where I read about that.

 

I think this might be one of the threads that led me to this solution.

https://www.corvetteforum.com/forums...oogle_vignette

 

This video pretty clearly shows exactly what I was trying to describe and what I did as well.

https://www.google.com/gasearch?q=cl...yx3UVFik4,st:0

 

Thank you very much tjed. I was leaning towards the EBCM which I have done before or simply just cleaning grounds. Checked the battery and all was good. Will take out that ignition switch and go with a new one. Give me time to play with the old one in case I just destroy it. I greatly appreciate you taking the time to help out. The links you posted are absolutely stellar in description with pictures. Will keep everyone posted as to what I do and how it turns out.

 

So this morning I replaced the ignition switch with one I bought off of Amazon. It worked. When I first started it, it did not. ABS light on, service traction system message on the DIC and the AC did not work. Then the car would not start at all and the module in the right door (I think. could have been something else but that is where the noise came from). Mad as hell for doing all of that for nothing. Only got a click when I turned the key. Had the door open for a couple of hours so I figured I drained the battery working on it. Should not have went dead in just over 2 hours so I will address that today as well. Hooked up the jumper cables from my truck and it cranked right up. AC kicked right on, ABS light off, no messages on the DIC. I went through the codes and they were all history codes. Cleared them all and now I have a clean dash and a great working Corvette. Thank you tjed for the information. The key is a bit hard to turn, but I think that is because I did not seat the ignition correctly as there is a gap between the dash and ignition bezels. Will correct that later as we are just under triple digits here today. If anyone else does this job and it initially does not work, shut it all down, clear the codes and try again. I have driven it a couple miles and cycled the ignition at least 5 times and no issues. These cars will definitely test your patience. Enjoy your Corvettes daily and put them on a trickle charger when not in use.

 

Really happy to hear you got it working! I’m convinced a dirty corroded ignition cylinder is a huge culprit for C5 electrical issues.