It may have been overcharging since you saw 17 volts. If it was really up to 17 volts the PCM may have put it in a limp mode to protect the electronics from the high voltage so it does not damage any of the electronics. They use and electronic throttle body that is a fly by wire system as the throttle body has and electric motor in it to control all phases of the gas pedal. It also has 2 TPS so it can double check what throttle posistion the driver is asking for. I cant say that was your problem but these PCM's are very smart today and if it was overcharging the PCM may have put it in the limp mode to protect the electronics from to high of voltage. Did the charging volts come back to normal (13 to 14.8) when it ran OK again ? If it did then it may have an overcharge condition at times and the PCM controls the charging rate. Course it could also have the field ground side wire touching to ground at times. Ron