charging problems

2001 CHEVROLET 3500
120,000 MILES • 8.1L • V8 • 4WD • AUTOMATIC
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JMONTHEI
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  • 2 POSTS
New alternator, new battery, The 2 small wires that come from the PCM have 0 voltage. is the PCM bad or is there something else in the equation that i can do?
Dec 6, 2019 at 3:46 PM
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94 TRANSAM
  • CERTIFIED EXPERT
  • 680 POSTS
Hello,
Make sure the fuse in the diagram below is good.
Trace the pink wire and make sure you have voltage at both ends and no reading to ground.
Make sure you have 12v at both ends of the black/white.
Make sure the gray to dark green splice under the dash is good.
Confirm voltage on dark green side of splice.
Confirm 0 volts on red at alt not just at battery to make sure its not a junction block issue.

Let us know what you find out.

Rich
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Dec 6, 2019 at 6:34 PM
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JMONTHEI
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All that checked out. The two small wires coming out of the alternator have no voltage to them. And on the 4 pins on the alternator it’s the middle two that the wires go to. Where do those wires go?
Dec 9, 2019 at 7:59 AM
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94 TRANSAM
  • CERTIFIED EXPERT
  • 680 POSTS
The brown and gray go to the PCM. I would pierce the wires about an inch from the plug and see if you have voltage there and the wires are broken at the plug. If not check them at the PCM. Also test the alternator case to the negative battery terminal and make sure the alternator is grounded.

If you have no voltage at the PCM then it is bad.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Rich
Dec 9, 2019 at 4:49 PM