Re: Electrical problem
That sudden drop is quite strange, since the battery voltage will not drop like that. Do you have a volt meter to check the voltage on the battery itself? Is this indication the same as you have on the gauge?
I expect the regulator to be a part of the PCM and also the voltage indication comes from the PCM. Check the connectors on the PCM for moisture and/or corrosion (disconnect negative battery connection before removing the PCM connectors).
If this doesn´t help, remove the thick wire from the alternator and isolate it with isolation tape to prevent a short. If you now run the engine, what is the voltage indication?
Since the check engine light is on, is there any fault code set?