2003 C5 convertible, 50,000 miles, new to me 4,000 miles ago. Check engine light came on during a 5 mile drive home Saturday night, no loss of performance. Went for a drive Sunday and check engine light comes on again and then shortly after the ABS and stability control warning lights come on and all of the fuel, water, oil gauges peg. Get home and put the top up and discovered the driver's window won't operate, in fact none of the controls in the driver's door will function. Went into diagnostic mode today and pulled one to 4 codes from each modules except the AO-LDCM which indicated "no comm". The only hard code was in the HVAC module and it was P1160 H C, and would reset as soon as I cleared it. I didn't have the engine running. Started it up the DIC said service soon, Tire pressure monitor. I haven't taken if for a drive since clearing the codes. The driver's door controls seem like the easiest place to start since it is a constant fault and I'd suspect there are not too many points of failure that would cause this. Any suggestions on where to start? Would the no comm to the LPCM cause the door control issue? Thanks for any help, I used to work on GM ECM's professionally but my last year doing that was 1989 before OBD2 came out.

 

I’d start checking your power and grounds at the module for a No Comm !!

 

check the connector in the rubber piece between the door and frame

 

I touched it and everything in the door started working! Thank you! I cleared all of the codes and they all stayed clear. Waiting for the roads to dry off a bit before taking it for a drive. Is the connector actually in the rubber piece as in I don't have to take the door panel off to get to it?

 

As you already found out, it seems your no-comm codes and other symptoms were the consequence of a corrupted Serial Data Bus.

This is a well known problem and you can read more here. It is usually caused by bad contacts in a connector within the doors' rubber accordion that could corrupt the Serial Data Bus, impacting the normal data flow.

The Serial Data Bus goes through each rubber accordion to the corresponding door control module. The female pins of the connector on that wire harness get deformed (see picture below), causing bad contacts and loss of communication/corruption in the Serial Data Bus and affecting all modules linked by it.



Check the connectors for deformed pins. If bad pins are found you would need to repair the connector (disconnect the battery first), fixing the female pins so they have a positive grip, or replace it. If you want to replace the connector take a look at this post for some ideas.