PCM stops controlling alternator?
Thread Starter
Joined: Sep 2004
Posts: 3,148
Likes: 12
From: Downers Grove, IL
PCM stops controlling alternator? I have a 2001 tahoe 5.3L swapped into my El Camino. Last week the alternator started this thing where it would just stop charging. I had it tested a few times and it always tested good. Today I decided to check the 2 wires from the PCM that control it. I had made sure that the wires and connections were good last week, today I checked the voltages while I drove. I checked the battery, charge indicator, and field voltages today as I took it for a ride. The alternator was charging and the battery was consistently at 14.4V , the charge indicator wire stayed around 11.3-11.8V and the field voltage was around 2-5V. It charged just fine for about a half hour, then I couldn`t stand it anymore, I noticed that before it would charge ok until you stopped and shut the car off then it would not charge. So that is what I did, when I restarted the car the battery voltage dropped to 12v, the charge indicator wire went to 2.5-3V and the field voltage went to 0.03V for the rest of the ride. Now I am thinking it must be a computer problem since the computer supplies the voltage to the charge indicator wire and the field wire.
Has anyone else seen the computer stop supplying voltage to the alt? I don`t think it is a bad connection or broken wire since I didn`t move or wiggle anything, I just shut the car off and restarted it. Is my PCM junk or is there something else I can check?
Has anyone else seen the computer stop supplying voltage to the alt? I don`t think it is a bad connection or broken wire since I didn`t move or wiggle anything, I just shut the car off and restarted it. Is my PCM junk or is there something else I can check?
Can you get into the pcm and verify the "L" and "F " field errors haven't been disabled for the alternator. Also make sure the gounds are of adequate size and located as close as possible for the pcm and motor.
