I am constantly haunted by codes and warning lights lately ... here is my new issue. When starting the car the AC does not turn on right away ... no lights whatsoever shown on AC unit and then a minute or two later it "powers up" and blows cold air just fine. Usually stays on for a while and with then randomly "turns off" (no lights on it, no ac blowing) some point while driving, and will turn back on a few minutes later. I did stop to check codes when it was out and HVAC reported "no comm". Later after it turned back on it gives a history code of B0338. Another signature is each time it stops working the ABS light also comes on ... the ABS light goes off the second it starts working again ... weird.

Intermingled with the above issue is random traction control light coming on as well as Service Engine Soon almost always coming on briefly when I first start the car but this goes away with a minute or so almost all the time. I also checked the codes with engine on when the traction control light was on and it said "no comm" for this also and then I get the history code below when turning car off.

A summary of my codes over the last week are:

PCM - P1571, P1689
TCS - 1277
BCM - B0432
SDM - U1040
IPC - U1040
HVAC - B0338

Uuuuuggghhh, this is getting old. FYI I already did the absfixer.com rebuild to fix previous ABS/traction control lights which seemed to fix old issues and now got these.

Any ideas ???

Thanks in advance ...

 

PCM - P1571 - Traction Control Torque Request Circ
PCM - P1689 - Traction Control Torque Delivered Circ
TCS - C1277 Requested Torque Signal Circ Malfunction
BCM - B0432 Rear Defogger Relay Circ
SDM - U1040 - Loss of Comms with TCS
IPC - U1040 - Loss of Comms with TCS
HVAC - B0338 - Inside Air Tmp Sensor Open

All of these look like (and your symptoms sound like) wiring connections.

I'd check two places .... first I'd check the connections to the EBCM and make sure they are clean, and that the connections are on the EBCM properly .... it is possible you have a loose connection.

The other place I'd check is in the passenger footwell ... check the carpeting and the area around the BCM and fuse box for water. It sounds like the connections for the computer network may be having trouble, or the HVAC power supply is flakey. The fact that the ABS light comes on when the HVAC goes out sure sounds like wiring somewhere is getting "crossed"

 

I am now wondering if a low battery might have contributed to this. I was out of town for a little over a week and my red top Optima has drained on me in the past a couple times while sitting for a while. The car started ok but could tell it was "weak". Makes sense that some of these codes may have been thrown when it was weak but doesnt make total sense as I do have an hour commute to and from work which it should have charged and it still turned off a couple times randomly. W ealso had temps about 110 degrees so weak battery and heat may be contributing to this ... dunno ... weird. Today, the AC still did not immedialtely come on when starting but so far it has not turned off on me again like it was before ... maybe it is slowly charging to a normal state and thus why working "better" now. Might just try a new battery for the heck of it. My traction control light is also very random ... usually will only come on when first starting or it wont come on at all.

 

I'd definately do a new battery. I've seen numerous posts from people with the red tops where they have died in under a year ..... not good.

Also, still check the pasenger footwell area for water .... there is an "udder" in the engine compartment that drains water away from the A/C system, and if it gets blocked that water backs up and unfortunately pours into the footwell area. Now I know you don't use much A/C in AZ ..... but check it out .....

I'd recommend the Sears DieHard line as a good choice, and Napa apparently has a good reputation for their "name brand" batteries. Interstate has a reasonable reputation .... and the AC Delco's aren't bad either.

The biggest problem with "late model" cars is that they HATE to sit. When you park your Corvette, lock the doors with the fob and walk away .... guess what ... both the BCM (which is running the SECURITY system) and the RFA (the radio receiver/transmitter waiting for your key fob to issue an UNLOCK transmission) stay powered up, and draining your battery.

The RFA shuts down after about 7 days of waiting for you to show up. When it does that the only way to unlock the car is mechanically with the key. The BCM does not shut down .... it continues to draw power until the battery is dead.

Ideally car makers should have 2 batteries in a car .... one for running the car when the engine is off (supplying the BCM and RFA) and the other battery strictly for engine starting ..... so even if you left the car parked for several months and the first battery was dead, you could still start the car with the starter battery and then let the alternator charge them both as you drive.

 

Thanks for all the help ... its looking more and more like the battery. Today at lunch everything was fine as ac kicked on immediately and stayed on plus no traction control light. I will still check for signs of water backup and look into a new battery.

 

Watched the battery some more and it held its charge fairly well. So, have extended warranty and decided to take it in and let them figure it out from here. Ended up being a bad ignition switch causing all this and the warranty company actually paid up this time .

 

Just wanted to thank all of you for the help you didn't realize you were giving. Had similar problem with my ABS and Traction Control, I tightened the connection on my battery cables and the message has dissapeared. Thanks!