P1637 charge system fault issue
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Racer
Joined: Sep 2011
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P1637 charge system fault issue
i was driving today and out of nowhere my voltage dropped and the dic threw a message saying charge system fault. luckily i was near my house so i made it home on such low voltage, had my alternator tested and it is working fine. are there any fuses i need to check? and where exactly are the grounds related to the charging system.
Thread Starter
Racer
Joined: Sep 2011
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no stock manifolds. at a glance the starter wires all looked good. battery connections are tight. but im not sure where the grounds are to check or the fusable links. although there was some welding done to the rear frame recently.
Last edited by seansz28; Jun 3, 2014 at 01:31 PM.
Racer
Joined: Jun 2004
Posts: 270
Likes: 67
From: Montana
I had the same problem (P1637). The alternator checked out good, but after checking everything else. I went back to the alternator (100K+ miles), I found that brushes were almost gone. Changing the brushes and voltage regulator fixed the problem.
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Racer
Joined: Sep 2011
Posts: 312
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Alternator puts out 14.5v on the test bench. In car does nothing. Battery wire and battery showing same voltage bypassing starter has no effect. L terminal has no resistence and is only putting out .8 volts while running. Is pcm fried?
Thread Starter
Racer
Joined: Sep 2011
Posts: 312
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the three terminals on the alternator at the plug are L(generator turn on signal in the schematic you provided ) ,F,and S. from my understanding the L is supposed to be 5v from the ecu to turn on the generator. F is for the pcm to see the alternator duty cycle and S goes to the starter for a 12v always on source. jumpering the S terminal wire to the battery positive post should rule out starter wire. and the L wire ohm'd ok. but while on the L wire (should be 5 volts from what iv read) is only putting out .85v
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Thread Starter
Racer
Joined: Sep 2011
Posts: 312
Likes: 0
the three terminals on the alternator at the plug are L(generator turn on signal in the schematic you provided ) ,F,and S. from my understanding the L is supposed to be 5v from the ecu to turn on the generator. F is for the pcm to see the alternator duty cycle and S goes to the starter for a 12v always on source. jumpering the S terminal wire to the battery positive post should rule out starter wire. and the L wire ohm'd ok. but while on the L wire (should be 5 volts from what iv read) is only putting out .85v