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crouse
08-18-2010, 07:33 PM
On Tuesday I helped a friend change the alternator on his 1999 Chevy Suburban. Like idiots, we forgot to disconnect the battery and when we were removing the nut that holds the big wire on the back of the alternator, we got a little arcing between the wrench and some bracket near the alternator.

Anyway, we installed the new alternator and it started and ran just fine. He drove it down the street and back without any issues. We let it idle for about 15 minutes since the battery was a little low, and he said when he went to go home, it was ran really rough like the engine was going to kill. Today, he said it ran even worse.

Is it possible we damaged the control module (not sure what Chevrolet calls theirs). Seems weird that it started and ran just fine at first.

Any help would be appreciated.

Thanks,
Curt
BAD MERC
08-18-2010, 07:59 PM
Disconnect that same wire and see if it has voltage on it. If you blew a main fusible link - you'll be starving the truck of voltage and causing all the electronics to go berserk.
crouse
08-18-2010, 08:30 PM
Will do. thanks for the help.
SpartaPerformance
08-18-2010, 08:35 PM
If that doesn't work you might have set the ECU into a limp mode. Most GM's that have a positive terminal jumper separate from the battery can easily have this happen to them, it mostly happens if you jump the car from the battery and not that separate terminal. If you have a hand held scanner hook it up and clear any codes.
crouse
08-19-2010, 06:29 AM
It's now running fine but the CEL is on. He is going to bring it to O'Reilly's and have them hook up their scan tool to determine the problem.

Would the Limp Mode clear itself?
Blackened300a
08-19-2010, 06:36 AM
It's now running fine but the CEL is on. He is going to bring it to O'Reilly's and have them hook up their scan tool to determine the problem.

Would the Limp Mode clear itself?

Yeah when it detects nothing is wrong but the CEL will light because it detected something that put it in limp mode in the first place.
crouse
08-19-2010, 07:15 AM
Thanks for all the help. I was worried I killed the ECM when I shorted out the alternator. Curt