Can't find any comments on this problem: Intermittent electrical failures.
Sometimes on startup especially after sitting in sun for couple days (I'm in Hawaii with no carport or garage) the engine will start but some of the dash gauges won't work (oil pressure, fuel level, water temp), along with no elec windows, and no a/c (fan runs but no cooling); in addition many of the dash lights will be on: ABS, traction control, service engine; also getting reduced power warning and shocks inoperative (I have installed aftermarket shocks and shorting plugs).
During this mode, the lights work, as do the windshield wipers, and power door locks.
Car has been at garage for week and none of the techs seem to have a solution. Only recommendation to date was replace the PCM.
Does that seem reasonable when it is behaving as if it was an intermittent ground failure?
Any help would be appreciated.
professor jimB

 

Aloha!

I would suggest to put on hold the PCM replacement until some troubleshooting is done...

Make sure your battery is fully charged and it wouldn't hurt if you could have it load-tested. Lots of problems are created when the battery is not 100%.

You should start by checking your codes. Write them down, then clear all codes, go for a ride and see if any one returns. Next time this problem happens, before shutting off the car, retrieve all codes while the engine is running.

Most, if not all, of the problems you mentioned are typical of a corrupted Serial Data Bus. Modules, sensors, gauges, etc., communicate through the Serial Data Bus, and it seems something is not allowing the normal data flow. Once the Serial Data Bus is corrupted all other devices that use it get affected.

This problem has been extensively documented by Bill Curlee and you can read more here. It is usually caused by bad contacts in a connector within the doors' rubber accordion.

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



You can troubleshoot by opening the Star Connector 2 by the passenger's foot well, which isolates both Door Control Modules along with the Left Seat Control Module and, if commucations are restored to the other modules, then you have your culprit(s).

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.

If connectors are fine, then the problem could be downstream the connectors up to the door control modules, or in the wiring/connector for the driver's seat up to the seat control module.


The Star Connector 2 is the one that has four wires. To perform this test you have to pop the top shorting strip off the top of that connector.

 

Your explanation may be instrumental in helping us find this gremlin. I sent copy of your message to the tech working on the car and hopefully he can use it to find and fix my problem. Whatever the result, I want to thank you immensely for taking the time to respond and include links and pictures. Your effort really makes me appreciate our Corvette community. Thanks again.
professor jim

 

@professorjim Glad to be of service! Let us know how it goes


NOTE: I would suggest that instead of using a generic code scanner, to take advantage of the C5's built-in capability of displaying codes through the DIC. Generic tools can only display generic codes and not platform-specific ones.

The Diagnostic Display Mode is entered with the following procedure:

1. Turn ON the ignition but don't start the engine.
2. Press the RESET button to turn OFF any warning messages. (i.e. door open, trunk open, etc.)
3. Press and hold the OPTIONS button
4. While holding OPTIONS, press FUEL button four times within a 10-second period.

 

First thing I would do is redo all the ground points on the car.
Charge the battery. Doing those 2 solved all my issues

If that doesn't help then start looking up codes ect.

 

Your car is HOT!

 

I'd go with SuperTom above. I'm no tech guru but I am aware that C5's are very sensitive to grounds/voltages etc. Starting with grounds/battery is a cheap place to start and maybe will help your problem if you luck out. Good luck fixing!

 

All of those symptoms can be caused by a failing ignition switch. Burned contacts within the switch sometimes make adequate contact, sometimes not. Often no codes or no relevant codes.

When the second ignition switch began failing on my car, I saw ABS, traction control warnings, service engine; also reduced power warning. A clue to a failing ignition switch is that turning the key to clear off and restarting may clear some or all of the symptoms initially until the switch completely fails.

 

Moved to C5 Tech.