P0621

DTC P0621

DTC Descriptor

DTC P0621

- Generator L-Terminal Circuit

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview

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 ON the field circuit ON and OFF. The ECM/PCM monitors the state of the generator turn ON signal circuit. The ECM/PCM should detect low voltage on the generator turn ON signal 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 generator turn ON signal circuit. The ECM/PCM performs key ON and RUN tests to determine the status of the generator turn ON signal 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.
OR
* 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.
* Using the scan tool Clear DTC Information function can clear the DTC.

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 and ground.

• If greater than the specified range, test the generator turn ON signal 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 and ground.

• If less than the specified range, test the generator turn ON signal circuit for a short to ground, an open, or a high resistance. If the circuit tests normal, replace the ECM/PCM.

4. If all circuits test normal, replace the generator.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Generator Replacement (RPO LSJ) Generator Replacement (RPOs L61/LE5)
* Control Module References for ECM/PCM replacement, setup, and programming