2000 Firebird - Electrical - Grounding problem

kat5469 · #1 08-15-2007, 02:53 PM

My factory radio/cd will stop working and the power windows will not work too. This is not a constant problem, so when I take it to the dealer they can not trace the problem. They believe it is a grounding problem but cannot figure out where. I'm not sure if there are any other items not working when this happens. Sometimes it will go on for hours and sometimes for seconds and of course never long enough when it is at the dealer. I've also noticed on occassion my car will not start and it is not the battery, cables, starter, alternator, etc. It's like no power what so ever. I wait and re try a few times then it starts. This all first came about when I was having problems with the window motors, that have been replaced several times. Then I finally tied the radio and windows together after I replaced the motors.

cardboardpimp420 · #2 08-15-2007, 06:03 PM

i know you said that they are not the battery cables, but im gonna ask this question anyway...have you checked the connections on the battery cables where the cables actually connect to the car?

ikeyballz · #3 08-15-2007, 06:44 PM

+ are the terminals clean? what i had with my camaro and my sisters camaro, is that since they use side posts with plastic covers, you dont see the corrosion under the plastic cover! check those too..

kat5469 · #4 08-20-2007, 05:29 PM

Quote:

Originally Posted by cardboardpimp420

i know you said that they are not the battery cables, but im gonna ask this question anyway...have you checked the connections on the battery cables where the cables actually connect to the car?

yes, I have checked and cleaned the battery post. The dealer thought they figured it out last week and said it was the ignition switch and replaced it and took care of some wires in the junction, 2 days later the same problem but for just a few seconds and then again today for maybe a minute or so. This happens while I am driving.

kat5469 · #5 08-20-2007, 05:32 PM

Quote:

Originally Posted by cardboardpimp420

i know you said that they are not the battery cables, but im gonna ask this question anyway...have you checked the connections on the battery cables where the cables actually connect to the car?

YES!

ikeyballz · #6 08-20-2007, 07:42 PM

does it happen when you go over a bump/etc? or just..randomly? have you been blowing fuses? or it just sporadically goes out? and comes back on? when you're looking under the hood, can you spot any shorts/ burn marks/ melted wires?

when youre running the car and it happens, does your car shut off? (no power to spark plugs?)

LtWizzard · #7 08-26-2007, 04:16 PM

My Firebird 2000 has the same problem. It has been going on for many months now. Took it to the dealer, but they could not duplicate the problem since it is intermitent.

I will be just driving along and the radio and window controls will stop working. Sometimes for a few seconds, sometimes for many minutes. Using the lock/unlock swith sometimes restores power as opening and closing the door will, but I have not found a sequence that works all the time. Sometimes I just have to wait.

Since all power for both the radio and power windows comes from the body control module (BCM) either the BCM is bad or wiring from the module to the fuse block on the driver's side dash is bad. The dealer tested the BCM and said there were no error code, so the unit is good. But if the module has a relay within it, then a relay could be intermitent, but since the computer is runing OK, it would not register any errors. I could replace the BCM for $200, but that is an expensive gamble if I am wrong.

Any additional help would be helpfull. If I brake down and get a new BCM, I will let you know the results.

Charles

kat5469 · #8 08-29-2007, 11:49 AM

Quote:

Originally Posted by ikeyballz

does it happen when you go over a bump/etc? or just..randomly? have you been blowing fuses? or it just sporadically goes out? and comes back on? when you're looking under the hood, can you spot any shorts/ burn marks/ melted wires?

when youre running the car and it happens, does your car shut off? (no power to spark plugs?)

Yes, sometimes over bumps but not always, not consistent. Last time I took it to the dealer they said it was the Starter Switch they replaced it and let it run for hours and no problem, next day it cuts out for a second, 2nd day cuts out again, and now it does it all the time. I also found out that when the radio shorts out and the power windows don't work, the convertible top also does not work.....these are all that I have tied together....never any problems with fuses. They claim they found some problems with the wires to the starter switch. I had told them on a few occasions the car would not start and then it would.....all inconsistent so hard to detect.

kat5469 · #9 08-29-2007, 11:53 AM

Quote:

Originally Posted by ikeyballz

does it happen when you go over a bump/etc? or just..randomly? have you been blowing fuses? or it just sporadically goes out? and comes back on? when you're looking under the hood, can you spot any shorts/ burn marks/ melted wires?

when youre running the car and it happens, does your car shut off? (no power to spark plugs?)

No, the car never shuts off, don't see any bad or melted wires, and the car is back at the dealer today for at least the 4th time.

kat5469 · #10 08-29-2007, 11:58 AM

Quote:

Originally Posted by LtWizzard

My Firebird 2000 has the same problem. It has been going on for many months now. Took it to the dealer, but they could not duplicate the problem since it is intermitent.

I will be just driving along and the radio and window controls will stop working. Sometimes for a few seconds, sometimes for many minutes. Using the lock/unlock swith sometimes restores power as opening and closing the door will, but I have not found a sequence that works all the time. Sometimes I just have to wait.

Since all power for both the radio and power windows comes from the body control module (BCM) either the BCM is bad or wiring from the module to the fuse block on the driver's side dash is bad. The dealer tested the BCM and said there were no error code, so the unit is good. But if the module has a relay within it, then a relay could be intermitent, but since the computer is runing OK, it would not register any errors. I could replace the BCM for $200, but that is an expensive gamble if I am wrong.

Any additional help would be helpfull. If I brake down and get a new BCM, I will let you know the results.

Charles

The Dealer said they didn't find a problem with the BCM or wiring from the module. That was one of the first things they thought it was. Your problem sounds exactly the same as mind. I've not had any problems with the door locks. I would check them to see if they worked when the radio and windows would not and they always did and didn't seem to restore or change anything.
What dealer did you go to? I'm in Houston, TX.

LtWizzard · #11 09-04-2007, 04:34 PM

kat5469,

I took it to Bob Daniels, a GMC dealer here in Columbus, Ohio.

Today, opening and closing the door didn't help. It stayed off for a few minutes, and then on/off/on interment four or five times, then stayed on.

I am in electronics and computers, so I understand how the body control module works, but I am not privy to the logic tree that GMC uses that control the unit, so it is very difficult to troubleshoot. Here is what I have compiled so far:

The power staying on for the windows, radio and convertible top are options know as the retained accessory power (RAP) option, which is controlled by the BCM. There is a single wire between the BCM and the fuse block that holds the fuses for the windows, radio and convertible top. The BCM has some type of electronics control inside (mechanical or solid-state relay) that switches between power controlled by the ignition switch (on when ignition is turned on) and a time-delayed power (10 minutes) source, the RAP.

The BCM receives inputs from the door switches and the ignition switch. When the ignition switch is on, power is in normal mode and is feed to the line to the fuses. But when the doors remain shut and the ignition key is removed (after having been on and the engine running) the BCM selects the RAP power source, which stays on for ten minutes or until the BCM receives a signal from one of the doors when they are opened. At which time the BCM switches back to the normal ignition source, which has no power because the ignition switch is off (key has been removed).

Now the strange thing is that we both are losing ALL power while the ignition switch is on, which means something in the BCM is stopping it or the wire between the BCM and the fuse block is intermittently open. I have also noticed that the radio, etc. do not stay on as designed (i.e. the RAP option) when the ignition key is removed. This is also interment, but seems to happen after the power losses have occurred while driving. I believe this adds more support to my theory that it is something inside the BCM rather then an intermittent in the wire. Something is malfunctioning within the BCM that generates no error codes, but causes a disruption of power on the down side of the control source. I am starting to gain the courage to swap the BCM out and see it that fixes it. It will cost $200, but this intermittent stuff is driving me crazy. I listen to a lot of books on CD, so it is more then just music stopping and going.

Hope you can follow all that, if not, ask me some questions and I will try to clarify. Perhaps your dealer would be more willing to listen to you or read a copy of my replay. My dealer more or less was sympathetic, but had the attitude that if it wouldn’t do it for them, then it’s not broken and there is nothing they could do.

Good luck.

kat5469 · #12 09-05-2007, 09:44 AM

Quote:

Originally Posted by LtWizzard

My Firebird 2000 has the same problem. It has been going on for many months now. Took it to the dealer, but they could not duplicate the problem since it is intermitent.

I will be just driving along and the radio and window controls will stop working. Sometimes for a few seconds, sometimes for many minutes. Using the lock/unlock swith sometimes restores power as opening and closing the door will, but I have not found a sequence that works all the time. Sometimes I just have to wait.

Since all power for both the radio and power windows comes from the body control module (BCM) either the BCM is bad or wiring from the module to the fuse block on the driver's side dash is bad. The dealer tested the BCM and said there were no error code, so the unit is good. But if the module has a relay within it, then a relay could be intermitent, but since the computer is runing OK, it would not register any errors. I could replace the BCM for $200, but that is an expensive gamble if I am wrong.

Any additional help would be helpfull. If I brake down and get a new BCM, I will let you know the results.

Charles

I asked the dealer to chec the BCM again and they did, but decided to change out the control module for the windows, which so far so good. But when I took my car in last week the Service Engine Soon - light came on and was still on when I picked up my car, 2 days later it went off, then has come back on again.....but at least now my radio, window motors and convertible top motor all are working........

LtWizzard · #13 09-08-2007, 02:45 PM

When you say they replaced the window contorl module, was that the BCM or something else? Not sure what they ment by window control module since everthing is controlled out of the BCM on our model of Firebird.

Not sure why your check engine light would come on, especially since you had it at the Dealer. Hope it is something simple to replace or fix like an oxgen sensor.

Keep in touch and let me know if what they did really does fix the problem over the next few weeks. If they did change the BCM, I will do the same.

Thanks for the feedback! The Internet is wonderful when you have problems like this.

acaba · #14 10-13-2007, 08:17 PM

Kat,

I have had the same problems with my radio and windows going out intermittently for about 6 months now. If I listened carefully I could hear the relay in the BCM clicking every time the power cycled. I checked the connections and everything is fine, so I think the problem was in the BCM.

I finally removed the BCM and opened it up. I found that one of the solder joints was cracked on the relay that controlls the power to the window & radio fuzes. I tried to heat up the solder joint to reflow it, but unfortunately I put too much solder on the joint and shorted something out. When I pluged it back in I let the magic smoke out of one of the ICs. Now the windows and radio work, but the door lock button seems to be cross connected to the trunk latch and the fasten seat belt light. And one of the chips on the board is kinda cracked and has goo leaking out of it. Guess this just proves that I'm truly a mechanical engineer, not an electrical engineer!

Anyway, I will try to replace the BCM tomorrow or the next day and see if my radio and windows keep working and the problem goes away.

Aaron

LtWizzard · #15 10-23-2007, 08:39 PM

Aaron,
I suspected something like that as I had said in my earlier responses. I have noticed that since it has gotten cooler (I live in Columbus, Ohio), that the radio/windows are not acting up. That would confirm that it could be a crack in the PC foil. Heat expands, cold contracts, but then you know that if you are a mechanical engineer. My background is electronics, so I just might take a look at mine this weekend. Thanks for the replay and I will check back to see how things work out for you.

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