If the battery and alternator are not the issue then we need to monitor the PCM data with a scan tool to see how much the PCM is turning the alternator on and off. Basically the PCM does what is called duty cycling with the alternator. This means when you need more voltage, the PCM ramps up the output from the alternator and then when it doesn't need as much it brings it down.
More then likely the PCM is the issue at this point. The other possible cause is wiring which is why we need to use a scan tool to find out what the PCM is commanding the alternator to do and go from there.
Thursday, August 6th, 2020 AT 1:00 PM