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 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 PCM applies a voltage to the voltage regulator. This signals the voltage regulator to turn ON the field circuit ON and OFF. The PCM monitors the state of the generator turn ON signal circuit. The PCM should detect low voltage on 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 PCM should detect high voltage on the generator turn ON signal circuit. The 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 PCM detects high voltage on the generator turn ON signal circuit for at least 5 seconds OR during the RUN test the PCM detects low voltage on the generator turn ON signal circuit for at least 15 seconds.

Action Taken When the DTC Sets

* The 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 PCM will not illuminate the malfunction indicator lamp (MIL).
* The 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 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 PCM.

4. If all circuits test normal replace the generator.

Repair Instructions

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

* Programming and Relearning for PCM Programming and Relearning
* Generator Replacement (RPO LX9)