P0621

DTC P0621

Diagnostic Instructions

- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0621: Generator L-Terminal Circuit.

Circuit/System 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. The ECM/PCM monitors the state of the circuit. The ECM/PCM should detect low voltage on circuit when the ignition is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM/PCM should detect high voltage on the circuit. The ECM/PCM performs key a ON and RUN test to determine the status of the circuit.

Conditions for Running the DTC

Key ON Test
- No generator, crankshaft position (CKP) sensors, or camshaft position (CMP) sensor DTCs are set.
- The ignition is in RUN position.
- The engine is not running.

RUN Test:
- No generator, CKP sensors, CMP sensor DTCs are set.
- The engine is running

Conditions for Setting the DTC

- During the key ON test, the ECM/PCM detects high voltage on the generator turn ON signal circuit for at least 5 seconds.
- During the RUN test the ECM/PCM detects low voltage on the generator turn ON signal circuit for at least 15 seconds.

Action Taken When the DTC Sets

- The ECM/PCM will command the charge indicator and or warning message to be illuminated on the instrument panel cluster (IPC) and the driver information center (DIC), if equipped.
- The ECM/PCM will not illuminate the malfunction indicator lamp (MIL).
- The ECM/PCM will store conditions, which were present when the DTC set as Fail Records data only.

Conditions for Clearing the DTC

The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the generator.
2. Ignition ON, test for less than 1 volt between the generator turn ON signal circuit terminal B and ground.
-> If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the ECM/PCM.
3. Engine running, test for greater than 3.5 volts between the generator turn ON signal circuit terminal B and ground.
-> If less than the specified range, test the circuit for a short to ground, an open or a high resistance. If the circuit tests normal, replace the ECM/PCM.
4. If the circuit test normal, replace the generator.