Re: 2000 grand cherokee 4.0 charging
Then indeed the PCM seems to be the culprit. For whatever reason its seeing 9V coming from the alternator and it most probably puts the alternator field at max. Donīt continue driving like this, because it will harm the battery and can also damage other electronic equipment.
Not completely sure where the PCM gets the actual battery voltage from, but it seems to be pin 22 from connector C1 on the PCM or pin 12 from connector C3 on the PCM. I would measure the voltage on both pins from the connectors C1 and C3, to be sure that this voltage is the same as the battery voltage. If it is, then i would suspect the PCM at faulty.