Alternator & Regulator: Operation

The PCM maintains a system charging voltage of 12.9-15.0 volts. PCM determines a control voltage or voltage goal based on inputs from battery temperature sensor (ambient temperature near battery) and system voltage at PCM terminal No. 3 (Red/White wire). PCM compares control and system voltages whenever engine is running. If system voltage is less than control voltage, PCM will provide more ground to field circuit. If system voltage is greater than control voltage, PCM will provide less ground to field circuit.

If a problem is sensed in a monitored circuit, a trouble code is stored in PCM memory and the Malfunction Indicator Light (MIL) will illuminate (with a few exceptions). Trouble codes can be read using the MIL or with the Chrysler Diagnostic Readout Box (DRB).

NOTE: Trouble codes remain in PCM memory for approximately 50 ignition on/off cycles. A trouble code will be erased from memory if failure does not reoccur.

For certain trouble codes, MIL will illuminate and PCM will enter limp-in mode. In limp-in mode, PCM attempts to compensate for particular component failure by substituting information from other sources. This allows vehicle operation until proper repairs are made.