Faulty Generator (Alternator)
Generator harness is open or shorted
Generator circuit poor electrical connection
Faulty Powertrain Control Module (PCM)
Engine Light ON (or Service Engine Soon Warning Light)
With the engine running, the charging system warning indicator is off. The circuit from the battery B+ to the generator regulator is 13-15 volts. This voltage feedback is used by the regulator to maintain the battery voltage at the desired set-point. The S (stator) circuit (internal to the generator) is used to monitor generator operation. This circuit and other regulator internal conditions are checked by the regulator to allow the PCM to turn off the charging system warning indicator by sending a message over the Controller Area Network (CAN) bus to the Instrument Cluster (IC). The positive battery output (B+) circuit is the generator output supplied to the battery and electrical system. For dual generator systems, these circuits are duplicated. Both generator regulators send a signal to the Powertrain Control Module (PCM) to allow the PCM to turn off the charging system warning indicator. In dual generator systems, the PCM keeps the secondary generator in a standby state where it does not generate current unless the primary generator is generating full power and more current is needed to support the vehicle loads. This may make it appear that the secondary generator is not working when vehicle loads are not large. It is important to note that a normal operational state of the charging system is for the secondary generator to not produce current.