P0621

DTC P0621

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 serial data message to the instrument panel cluster (IPC) to illuminate the charge indicator.

DTC Descriptor
This diagnostic procedure supports the following DTC:

DTC P0621 Generator L-Terminal Circuit

Conditions for Running the DTC
^ No generator, crankshaft position (CKP) sensor, or camshaft position (CMP) sensor DTCs are set.
^ The engine is running.

Conditions for Setting the DTC
The ECM/PCM detects a low signal voltage on the generator turn on signal circuit for at least 5 seconds.

Action Taken When the DTC Sets
^ The ECM/PCM sends a serial data message to the IPC to illuminate the charge indicator.
^ The ECM/PCM will not illuminate the malfunction indicator lamp (MIL).
^ The ECM/PCM will store the conditions present when the DTC set as Failure Records data only.

Conditions for Clearing the MIL/DTC

Step 1 - Step 10:

^ The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using the scan tool Clear DTC Information function.