I wanted to post this for anyone who has a C5 and see if they’ve experienced this chain of events relating to ABS/TC/HVAC errors/problems.
I’ve searched and searched threads about ABS and HVAC problems and nothing is comparable to my situation so I wanted to throw this out there for the experts on here to chew on.

I bought a 2000 coupe 6-7 months ago knowing the service abs and traction control message/lights were on. I got a really good deal because of it.
I’ve driven it now for 6-7 months and I just hit the reset button everytime I get in it to clear them. I resigned to the fact that this might be the way it is while I own the car.

The second issue I’ve had is that my HVAC unit just goes out completely while driving (not the usual dim display issue, my display is bright) or the unit doesn’t come on at all when I first start it but a few miles down the road it comes on.

I then noticed one day that there seemed to be a correlation between the HVAC not coming on and the ABS/TC lights and messages. When the HVAC didn’t come on when first starting the car or when it went out while driving, the ABS/TC message would go away and then I’d get a “service vehicle soon” message, then when the HVAC came back on, that message would go away and the “service ABC/TC” message comes back and I have to reset it again. Sometimes when I first start the car, I won’t get the “service ABS/TC” message and every time that happens, the HVAC unit also doesn’t come on but I’ll get the “service vehicle soon” message… every time without fail. Then when the HVAC would start working down the road, the ABS/TC message and lights comes on and the “service vehicle soon” message goes away.


I then started to go into the DIC and clear the codes, of which I have the usual suspected ones you get with a bad EBCM. One time I noticed when I cleared the codes of the TCS and hit reset, I put my foot on the brake pedal and put a bit of pressure on it at the same time when the code cleared and I felt the ABS pulsate for a second, then the code immediately comes back and all the messages and lights for the ABS/TC....but also when my HVAC unit is not coming on, I noticed when I clear the TCS code(s), the HVAC comes on and starts working ….some kind of electrical correlation between the two??

Which brings me to last night… I cleared the codes in the work parking lot, then while driving home the HVAC unit went out, came back on and went out and came back on within a mile, then all was working as usual.

I parked it, went into the store, came back out and started the car, and no ABS/TC codes, lights or message. This was the first time since owning the car that I’ve never seen the ABS/TC message or lights come on. I then pushed the TCS button on the console and it turned off the TCS, and hit it again and it turned on like it was working normal. TCS light in the dash came on and off and the TCS-on, TCS-off messages came on like they should have. So I drive home for the first time since owning the car without the ABS/TC message lights on and unloaded the groceries, didn’t turn the car off, went back out on the road and tested the ABS, and it worked. The ABS pulsated and seemed to activate like it should. When the ABS activated, both the ABS/TC lights and messages came on and I then had to clear the codes. Since then I haven’t been able to get them to stay off and work normal again like last night.

At this point, I’m beginning to feel that there is not anything wrong with my EBCM. I think its electrical and something is making my codes come on which disables the ABS/TC. Any of the electrical gurus on here have any ideas?? I would appreciate any feedback.

I plan to clean the ignition switch and clean any and all grounds per the instructions on this forum as soon as I get time. Maybe it is one of those issues.?

Anyway, thanks for reading and I would like to hear if anyone else has had this experience.