Ive read many other posts and still cant figure it out. The traction contol light and abs light intermittently turn on. I get the tcs 28 no comm for awhile then have the 1277h code along with others. I did notice when these two light come on the air conditioner will not turn on and will kick off if the light turns off. I cleaned the two front black ground connectors and it seemed to help for a couple days??

 

Post your codes: http://www.c5forum.com/ayc/dtcdic.php

 

So here's the list. pcm-p1571h,p1689h. 28-tcs c1277h. 40-bcm b0432h. 58-sdm u1040h. 60-ipc u1040h

 

P1571, P1689 and C1277 are all related to the same issue. The PCM is supposed to see a continual requested torque signal from the EBCM. If it doesn't see that signal or the signal is out of its normal range the PCM will set Code P1571 which causes the EBCM to set code C1277 indicating there is an issue with the requested torque signal. The PCM is also supposed to send a continual delivered torque signal back to the EBCM so the EBCM knows what the PCM is doing. P1689 is set because the delivered torque signal out of its normal range. These codes can be due to a problem in the following areas: the PCM, the EBCM, the EBCM ground, the wiring between the two modules and voltage supply.

Since some of the repairs to this issue can be very costly I would suggest first checking battery connections followed by the EBCM ground. The ground you checked on the left front frame rail was for the BPMV and not the EBCM. The EBCM ground is located at G108 which is with G104 on the frame under the battery. From there I would start checking wiring harnesses between the EBCM and the PCM to see if something happened to to them. Also did somebody mess around with the PCM? I would also check the voltage supply to the EBCM to see if it is at the proper level at the EBCM connector. If the EBCM has taken a dump you will have to replace it, same goes for the PCM. This failure isn't the kind that can be repaired by replacing a relay in the EBCM which is what is done to correct the C1214 code.

The other code is for some other voltage related issue in the rear window defog circuit. The U codes don't necessarily mean anything unless there are other issues.

Bill

 

I finally had the time to check the ground under the battery and the voltage to the ebcm. Both seemed fine. Maybe the EBCM is on its way out but my question is. If the air conditioner will not come on while the ABS light is on the dash and turns on instantly when the ABS light finally turns off. Is there some fuse or ground common to both that maybe the problem?

 

Pull the ABS fuses (Number 5 and 52) and see what happens with the A/C. With no power the EBCM can't do anything. The only common power pickup for the two systems is the underhood electrical center which has the ABS fuses and the compressor fuse. They are both tied to the serial data link but I doubt one is sending a message to shut off the other.

Bill

 

Sounds like the ignition switch to me.

 

Ha, knew I'd find it.....


http://forums.corvetteforum.com/c5-t...ntrol-abs.html

 

Looks like I have a day full of checking to do.. Thanks for all the info. Ill let you know what I find

 

pulled the abs fuses and the air conditioner still will not turn on. checked the computer on the footwell and no broken or corroded pins. Pulled the plug for the ebcm and check voltage with ignition on and am getting 9.82v (is this low with engine off?). Battery is 6months old. with plug unplugged I checked ac again and still not working. Is there something I can do to check ignition switch?

 

Wow...I thought I had narrowed it down for you....and even provided a link, that described your exact symptoms, right down to the codes..

Here you go....good luck..

http://forums.corvetteforum.com/c5-t...ch-repair.html

 

yeah it looks like you hit it on the head. It looks like the switch is only 60$. guess i have my weekend project lined up

 

it just boggles my mind how an ignition switch can make the tcs not communicate and my a/c not work..

 

I have the ignition switch ordered. Should be here Friday. He said the ignition switch needed to be programmed. Do I have to have the dealership do this?

 

I'm having this issue now

Do you have the part number by any chance...or for that matter where ya ordered it from?

Thanks!
Michael

 

Where did you order the switch from? You really have to be careful with aftermarket replacments. I helped a guy last month, who changed his ignition switch (new from advance auto I believe), and it was missing a contact.....which caused problems with the BCM column lock circuit. In the picture below, you can see the missing contact on the aftermarket switch.

It does not have to be done at the dealer, if you have the ability to do the work yourself. You are just swapping over the lock cylinder to the new switch.

 

I never advocate just changing parts, and the whole point of providing the info, was to give you the most likely cause. Using the schematics and a meter is the best way to confirm the ignition switch is the culprit.

 

I thought it was a good idea after reading so many posts with this being the same problem Im having. It was 58$ from gm parts direct. Its worth a shot.

 

Sure it's worth a shot, but I always prefer to know exaclty what is wrong, so I know I'm replacing the part in question with confidence. It's a personal choice.....your money, your time, your car.

 

Did the ignition switch do the trick for you on this project? I am having the exact same issue with my '01, TCS and ABS light with no AC sometimes for 30 seconds after start, other times for the entire ride.