Circuit Description

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

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 the 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 IPC to illuminate the charge indicator.