Alternator & Regulator: Operation

The PCM monitors critical inputs to control fuel injection, ignition, emission and other engine management functions. The PCM also monitors several charging system related circuits:

Battery Feed To PCM
Alternator Field Control
Battery Charging Voltage (High And Low)

If a problem is sensed in a monitored circuit, a Diagnostic Trouble Code (DTC) is stored in the PCM's memory and the Malfunction Indicator Light (MIL) will be turned on (with a few exceptions). DTCs can be read using the MIL, Diagnostic Readout Box (DRB) or a generic scan tool.

NOTE: DTCs remain in memory for 50 engine starts. DTC is erased from memory if failure does not reoccur.

For certain DTCs, 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.