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Every once in a while my c5 throws a bunch of lights like the traction control, abs and check gages while all the gage arms go to the worst side of the gage and the radio turns off. But when
I turn the car off and back on it work fine but lately it’s been doing it more often. It throws a bunch of “U” codes as well. Anybody experienced something like this and can help me out? There’s a pic of the gage cluster below.
The serial data bus is being corrupted like shorted to ground or power…we see a lot of the door module connector inside the rubber “accordion” boot which you will see when you open the drivers door has poor connections either loose or corroded terminals…you can look there or follow this guide if you have a scan tool…on the dash you normally see the gas gauge go to “E” and the water temp will max out…power windows don’t normally work either.
1) Locate the 2 Star Connectors to the left of the BCM and remove the buss bar or “comb” from star connector #2…it has 4 wires on it…see if the car starts…if no start go to next step.
2) Now remove the comb off the other star connector leaving both combs removed…make a jumper wire and jumper the BCM to PCM…light green to dark green wire….if car starts you have a module other than the BCM and PCM on star connector #1 pulling the data bus down….if car still doesn’t start the module pulling the bus down is either the BCM or PCM…go to next step.
3) Take your jumper wire and connect from the purple wire (data bus wire) to the PCM (dark green wire)…now with your scan tool see if you can communicate with the PCM…if you can now communicate the PCM is good and issue may be the BCM…to see if the BCM is indeed bad take the jumper wire and connect the jumper now to the BCM (light green)…with a scan tool that can communicate with ALL modules (NOT a code reader) and if you can’t communicate we can “assume” BCM is bad…for single module “no comm” you want to check the powers and grounds to that module.
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Next time it does this while the car is running open the doors and jiggle the wire accordions/boots. If your lights and warnings go away then the problem is in there. Mine does this every now and then but I just haven't gotten around to fixing it.
Loss of communication codes
