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I had some poor start issues (slow cranking) and without doing any troubleshooting I replaced the battery. Fixed the issue immediately.
I just had the car not start, no gauges, "Reduced Engine Power", "Low Fuel", Service Active Handling", no power windows, no power lock...couldn't even open the trunk.
Clearing the messages and checking codes showed every group with "No Comms"
A few minutes later, the car would start with a healthy crank - but still no gauges and all the same error messages.
Sounds like the “infamous” serial data bus issue !!...when a module such as a door, HVAC, BCM etc loses a power or ground that power or ground finds its way onto the serial data wire which allows all modules to communicate with one another...the connection inside the rubber “boot” between the driver door and body may be bad causing this...open the driver door and shake the boot and see if things go back to normal...if not we can try something else !!
It looks like moisture is the culprit; I definitely have some level of leakage on the passenger side and the carpet was pretty damp last night. I put down a dryer and a fan just to take care of that...but it appears to have also addressed the issue.
I guess I need to invest in finding that leak. I know the drains are clear as I just cleaned them out.
I thought the same as C5 Diag but you stated that the passengers side was wet... BCMs DO NOT like moisture. If it got wet, it could cause the exact issues that you had. FIX THAT LEAK! If its a FRC, its most likely the roof to windshield to pillar sealing compound getting hard and shrinking. ALL FRCs will experience this in their life time.
When the BCM dries out, it will work normal again.
HOWEVER, ALL C5s can experience the door wiring harness 6 pin power connector female pin issue C5 Diag was discussing.
PLEASE do not rule that out as it is a VERY common C5 issue. More common than the FRC roof seal leak!
03 Z06: NO COMM on all codes
