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International Automotive Technicians Network
Re: GM charging system, codes P1637 P1638
Posted to Technical Discussion Forum on 2/24/2017

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The alternator "L" wire is brown to the pcm connector 2 pin 15 Charge Indicator Control

The alternator "F" wire is Grey to the pcm connector 2 pin 52- Generator Field Duty cycle signal.

The red w... Login to read more.