Electrical Issues
 

This is my first post on these forums, I'm kinda hoping the MC community can give me some insights. I'm having some extremely strange issues.

I have a 2000 MC LS with the 3.4L v6

This all started about 5 months ago. My airbag light came on when starting the car. While the airbag light was on, my seat belt light would not come on and the chimes to indicate a seat belt was not buckled would not sound. I shut the car off, turned it back on and the light did not come back on, other than its normal flashing when the car is started, and the seat belt light and chimes returned. This happened a couple more times randomly, not on every start. Each time, shutting the car off and restarting it would make the light go off.

Then the light started to come on every time the car was started, and a restart did nothing to fix it, HOWEVER randomly while driving my ABS light, Brake Light, and Battery Light would flash for about 2 seconds, the airbag light would disappear, then the other three lights would disappear like nothing ever happened, and everything returned to normal. I took it to a dealership, they said that the module that controls those warning lights was bad, and offered to order the replacement module as they were not carrying one. I decided to wait on it until I had the 400 extra dollars required to do the repair. But before I could have the part ordered, the entire issue just disappeared, and that airbag light issue has not presented itself since. Its been about 3 months. I have not had that module replaced.

The reason I bring that story up is because I'm wondering if its related to my newest set of issues. About 2 months ago, I finished up with work and went out to my car, tried to start it and it would not turn over. The click of the starter could be heard, and all my dashboard lights went off, my radio went off, but it wouldn't turn over. 15 minutes and about a dozen tries later, it started up as if nothing was wrong. Since then this has happened 4 times, each time the same deal, randomly within 20 minutes from the first attempt it would turn over like nothing happened.

I've had a couple of infrequent instances (about 3 or 4 times) where the security light will come on and stay on shortly after starting the car. This started during the issue I had with the airbag light, and the last time it presented itself was about a month ago.

Last week, I had the battery tested and replaced. The test was showing the battery putting out about half the power it normally should, and I thought maybe that would explain the starting issues. I have not had an issue with the car not turning over since (Doesn't mean much as its only been a week). But just this morning after pulling out of my driveway, the car completely lost electrical power for about half a second, long enough for the car to shut off while I was driving down my road.


My question is do you think that these issues are related to one specific problem? And if so, what?

I was thinking a bad ground could be causing some of the problems, or maybe even the module that the dealership wanted to replace months ago?



Sorry, I know this is a long post.

That module they wanted to replace. Was it the BCM?

Random electrical problems that happen at odd times can be the BCM. The security issues you mention could also be the passlock system, but that shouldn't affect the other things.

I might have to agree with them that the BCM may need replacing.

I am unsure if it was the BCM. I had another garage try to diagnose the airbag light when it came on initially, and he said that he couldnt even diagnose the problem because he couldnt access the module to receive the code. He did however say he could see that there was a code stored.

Where is the BCM located on this car?

I can check to see if it indeed was the BCM that the dealership found at fault, it should be on my work order documentation that should still be in my car.

Checked for my documentation, It's not in my car. However I do now have a new issue.

Went to turn my car on just a few minutes ago and it wouldn't turn over, same deal as the other 4 times, however this time, when i turned it all the way off, and put it back in the run position to wait for the fuel pump, the only dashboard light that came on was my check engine light. It's acting like the battery is dead, power windows arent working, inside lights aren't coming on, and after trying anything requiring power (ex. power windows) the needles on all my gauges jump up and down in rhythm with a faint noise coming from behind the dash.

You replaced the battery, how are all the connections?

I would bet it's not the BCM, but rather your ignition switch. Pretty common issue on these cars

You can take it apart and clean it (and apply new dielectric grease) or simply replace it (not the cylinder, the actual ignition switch)

BBEngineer

Ignition switch killing the Airbags and seat belts?

The airbag/seatbelt issue may be tied to the ignition, but more likely a corroded connector on one of the seats. I guess it could be a bad SDM if the connectors look good

The airbags aren't routed thru the BCM at all, so it's not likely a BCM issue either

BBEngineer

Gotcha.

Listen to BBE, he's an electrical genius with these cars :)

Thanks for the replies guys. On my lunch break I went out to check the battery connections and the negative was indeed loose. I thought I had checked it after the battery was replaced but apparently not well enough. I tightened it up and it started right up.

That explains the issue with it being dead this afternoon and completely loosing power this morning. I haven't had any of the other issues since the battery was replaced, so I think for now things are looking good. I'll keep these other suggestions in mind in case these issues rear their ugly heads again.

I appreciate it guys!