Circuit Description

The engine control module (ECM)/powertrain control module (PCM) uses the generator turn ON signal circuit to control the load of the generator on the engine. A high side driver in the ECM/PCM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. When the ECM/PCM turns ON the high side driver, the voltage regulator turns ON the field circuit. When the ECM/PCM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.

The ECM/PCM monitors the state of the generator turn ON signal circuit. With the engine running, the ECM/PCM should detect a high generator turn ON signal circuit, or when the charging system malfunctions. If the ECM/PCM detects a low generator turn ON signal circuit DTC P0621 will set. When the DTC sets, the ECM/PCM will send a class 2 serial data message to the instrument panel cluster (IPC) to illuminate the charge indicator.