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Discussion Starter #1
97' 12V auto 4x4 3500. Stock minus 4" exhaust. The alternator wasn't charging while driving and truck wouldn't shift. After 3-5 miles of driving the alt would start charging and at the same time the truck would start shifting. When starting the truck, The Gen/ CEL/ wait to start lights would flicker, and not shut off, ever, and the trans relay clicks at a high rate. If i pull the relay the clicking stops, but the lights still flicker. I have replaced the batteries, alternator, checked and shined up the batt terminals. Unplugged the pcm wires on the fire wall. Still nothing has changed. :confused013:
 

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Discussion Starter #2
What would cause the trans relay to click repeatedly ? I'm going to check the ESS, and see if any wires are worn through.
 

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The PCM has internal self resetting circuit breakers to protect it.
Sounds like you have a short somewhere that's causing the breaker to trip off and on rapidly.
 

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Discussion Starter #4
i'll go do some running down and report on any success or failure
 

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Discussion Starter #5
So, I put it up on the lift and checked out the under carriage, everything is still in the factory wire loom. I unhooked the ESS and the black box on the back of the alternator and turned the key to on and still no change. I took out the engine fuse in the cab fuse panel, and that fixed it. Of course it wouldn't run, but it would start and then die. Put the fuse back in and everything was still the same... What is the box called on the alternator ? black box regulator
 

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What is the box called on the alternator ? black box regulator
It's just a connector block. The regulator is in the PCM.
 

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Discussion Starter #7
is that regulator replaceable, ?
 

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Discussion Starter #9
hmm. We had the pcm replaced about 2 months ago by a local shop. Looks like it's time to take it back.
 

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hmm. We had the pcm replaced about 2 months ago by a local shop. Looks like it's time to take it back.
It very well could be your PCM didn't need replacing back then and you still have the same problem, a bad connection at the PCM.
Just unplugging the old one and plugging in the new one could have temporary "fixed" the connection.
Poor connections at the PCM are a much more common problem than a bad PCM.
What happens is mechanics who only know how to diagnose problems when the computer tells them where to look figure if it isn't telling them anything then it must be the computer's fault.
 

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Discussion Starter #11
I'll give it a little dielectric grease and try again
 

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Check the female connectors carefully one by one while you have it unplugged.
I've run into some where the connector broke in half and were completely gone except for where the wire crimps in.
Sometimes just half of the connector is gone.
 
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