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Old Jul 25, 2009 | 03:35 PM
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Default Pcm problems

I had a meltdown in my car with the alternator, had the system checked and the guy said, with no certainty that the pcm may not be sending power to the alternator causing it not to charge the battery. Anyone ever hear of that before?
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Old Jul 25, 2009 | 03:39 PM
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Yup, but its most likely the "excitor" wire. The little tiny red wire that plugs into the top of the alternator. They go bad quite often. When you start the engine this wire tells the alternator to start charging.


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Old Jul 25, 2009 | 03:40 PM
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Get one of these and splice it in as high up into the wiring harness as possible.

http://cgi.ebay.com/ebaymotors/LS1-A...Q5fAccessories


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Old Jul 25, 2009 | 04:38 PM
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Thanks, do you know where to get one for lt1, forgot to mention that it is 96 T/A
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Old Jul 25, 2009 | 04:43 PM
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Don't know that. Do you have an excitor wire on yours?

I'm not really up on the LT1 stuff.

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Old Jul 25, 2009 | 04:44 PM
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yeah, the connector looks identical but i have a feeling it wont work for lt1. its the same 1 red wire connector.
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Old Jul 25, 2009 | 04:54 PM
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Originally Posted by noolah
yeah, the connector looks identical but i have a feeling it wont work for lt1. its the same 1 red wire connector.
Good chance its the same. The dealer could tell you. Or maybe someone can chime in here to tell you.

I would think you could start the engine with that wire unplugged, put a meter on it to see if your getting current, to see if thats the problem.

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Old Jul 25, 2009 | 05:10 PM
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well thats where we were confused. We put a tester on it and got 1 volt on it. I am unsure how many volts are needed. We checked the wire for continuity and that was ok too. I had it professionaly tested and they could not find a thing either. he said it may be the pcm. I am at a loss.
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Old Jul 25, 2009 | 05:34 PM
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Originally Posted by noolah
well thats where we were confused. We put a tester on it and got 1 volt on it. I am unsure how many volts are needed. We checked the wire for continuity and that was ok too. I had it professionaly tested and they could not find a thing either. he said it may be the pcm. I am at a loss.
I;'m not sure what output is needed on that wire, but if there's output I don't see how it could be the PCM. Maybe the wire is frayed or worn, thats the most common thing that happenes to them over time.

Try to find out what that output is supposed to be. Maybe post in the PCM/Diagnostics section for that answer.

Maybe there's corrosion somewhere. Maybe have the battery and alternator checked again, somewhere else for free. Charge the battery and drive it to an auto parts place.

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