Circuit Description

The ECM uses the generator turn on signal circuit to control the load of the generator on the engine. A high-side driver in the ECM applies a voltage to the voltage regulator. When the ECM turns ON the high-side driver, the voltage regulator turns ON the field circuit. When ECM turns OFF the high-side driver, the voltage regulator turns OFF the field circuit.

The ECM monitors the state of the generator turn on signal circuit. With the engine running, the ECM should detect a high generator turn on signal circuit, or when the charging system malfunctions. If the ECM detects a low generator turn on signal circuit DTC P0621 will set. When the DTC sets, the ECM will send a Class 2 serial data message to the Instrument Panel Cluster (IPC) to illuminate the CHARGE indicator.