This 1998 Chevrolet Cavalier came in with the complaint that the battery would go dead while driving. The battery and the alternator had been replaced and the battery light stays on while the engine is running. The first thing I did was to check the wiring at the rear of the alternator. The main battery lead had power on it at all times as it should have. The small red wire should have had 5 volts on it with the key on but it did not. I checked the wire at the connector carefully and found that it would stretch if, it was pulled with a modest force. Pulled a little harder and the wire separated.
Pretty easy diagnosis and replacement of faulty harness connector at the alternator. If you need to order this connector please click here. I replaced the connector and checked and found that the 5 volt reference voltage was still missing. Got to dig a little deeper.
In checking a wiring diagram I confirmed that the signal on the red wire came from the ECM. I knew that I have found problems with damaged wiring near these computers before so I decided to investigate. For some reason an engineer placed the ECM inside the lower right fender.
There are several screws and push pin retainers that have to be removed in order to take the splash panel off of the car. The right front ABS sensor wiring is also attached and has to be removed.
If you click on the following pictures you can see damage on a red and a gray wire.
My initial though was that mice had gotten in there and checked on the wires but there were no other signs. Instead I think what happened is that some one had jumped the red and gray wires together to possibly turn the charge indicator or battery light out in an attempt to keep the light off when the other wire at the alternator would fail to turn the alternator on properly (flashing light). Maybe it fell off or they pulled it back out. Anyway the red wire was severed and the gray wire was damaged. I repaired both and the alternator now charges properly.
I had to extend the gray wire in order to repair the damage, so I just looped it back around in the harness.
