Having electrical problems on a 2002 C5 I bought new. It started with extended cranking time and then starting on subsequent tries. Other times when I tried to start the gauges would dim with all the needles dropping and a low voltage warning. I was getting some codes "loss of communications" (1016?) to a lot of the different modules. I took it to a mechanic who says he checked all the grounds and load tested the battery but couldn't find the problem. He started having a new problem with the starter. The started solenoid would try to engage but then release, clacking like it had a low battery. If the gauges were performing properly the car would start and run. I would get an occasional "charging system fault error" on the dash display. He was getting ready to retire so I drove the car home. I pulled the BCM (body control module) and sent it in for analysis. They said it needed to be replaced, the CPU was damaged and couldn't be repaired. They sent me a refurbished BCM saying I was going to have to have the security system programmed. A little reading warned that before that was done the battery needed to be fully charged. I put my charger on the battery and got a warning back that the battery needed to be replaced. After replacing the battery the lock guy came and got the keys working but there was still the "charging system fault" coming up with the occasional low voltage warning as I recall. The airbag light warning was on and his programming system couldn't fix that, he was going to return with a different system. In the meantime I raised the car and started trying to figure out how to replace the battery cables which looked fine, the car has always been garaged. I discovered some wires which had been burned by the exhaust manifold. It looked like the alternator exciter wire, the solenoid actuator and one other I didn't know what was. I took it to a new mechanic. When he first started working on it he couldn't get it to NOT start and run even before he changed the wiring. My new mechanic replaced those along with the crank position sensor. Unfortunately, we are still having the same problems. I'm suspecting grounds again. Any suggestions? Anyone know which grounds would have anything to do with the gauge cluster? The alternator is still not charging either. Sometimes I saw a "service column lock" error with the refurbished BCM which was never a problem with 2002 automatics.

 

Is this something you are going to try to diagnose yourself or you just want to know “things that it may be “ ???…if you are doing the diag do you have a multimeter and know how to use it ??

 

I do have a multi meter but the car is at the shop right now. Given that the first mechanic didn't see the burned wires makes me question how thoroughly the grounds were checked. The second mechanic seems more than willing to listen to anybody.

 

The mechanic should know how to diagnose this without input from anyone !!...if he can't figure it out find a "diagnostic" shop or an auto-electric shop
and not a repair shop !!...sounds like 2 issues maybe and maybe one is a bad ignition switch...there are 2 IP fuses that can be checked to see if the switch may be bad or with a scan tool you ( your mechanic) can look at the "Ignition 1" data PID on the scan tool and see what the voltage is with the key on. With the alternator not charging you have to go to the starter solenoid and physically check (not it looks OK)...as far as the alternator not charging your mechanic has do a voltage drop check on the charging system...the B+ wire from the alternator runs down to the starter solenoid where the positive battery cable is also attached...if loose or corroded the alternator will not charge the battery..he should also look at the gray wire which is the F terminal at the alternator connector with a scan tool...with no load he should see around 20-25% duty cycle at that wire...with the electrical system loaded it should be near 100%...also with no load the amps from the alternator should be 15-20 amps if I can remember...if you see high amps with no load on the electrical system say 40-60 amps the battery is bad...the thin red wire on the alternator connector is the L terminal and you should see about 10.75 volts key ON....that wire goes the windings of the alternator to get things working.

 

Thanks, I will pass this on. The problem with electrical is that it could be multiple things and all you have to do is touch a wire by accident and everything is working again, for a while. He was leaning toward the ignition switch also.