Functional Description - Powertrain Control Module (Pcm)
The PCM communicates and commands the charging rate to the Smart Alternator via the LIN bus circuit. The PCM does not directly perform diagnostics of the Smart Alternator. However, the PCM does store and report the faults communicated from the Smart Alternator via the LIN bus circuit.
The PCM diagnostic monitor compares the reported battery voltage from the Intelligent Battery Sensor (IBS) to the currently requested set voltage from the Smart Alternator. A fault will be detected if the absolute difference (VOLTAGE_DELTA) between commanded Smart Alternator and actual IBS voltage values vary from one another above a calibrated threshold for an accumulated period of time. When the PCM determines there is a charging system failure the PCM will send a message to the Instrument Cluster to illuminate the check gauges lamp (if equipped) with the engine running.