P0621

DTC P0621 (DIESEL)

Diagnostic Instructions

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

DTC Descriptor
DTC P0621
- Charge Indicator Control Circuit

Circuit/System Description

The ECM monitors the state of the charge indicator control circuit. The ECM should detect a low circuit voltage when the key is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM should detect a high circuit voltage. The ECM performs key ON and RUN tests to determine the status of the charge indicator control circuit.

During the key ON test, if the ECM detects a high circuit voltage, DTC P0621 will set. DTC P0621 will also set if, during the RUN test, the ECM detects a low circuit voltage. When the DTC sets, the IPC will illuminate the charge indicator or a warning message will be displayed in the driver information center (DIC) if equipped.

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 detects high voltage on the charge indicator control circuit for at least 5 seconds. OR during the RUN test the ECM detects low voltage on the charge indicator control circuit for at least 15 seconds.

Action Taken When the DTC Sets

DTC P0621 is a C type DTC.

Conditions for Clearing the DTC

DTC P0621 is a C type DTC.

Reference Information
Schematic Reference

Starting and Charging Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Charging System Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Ignition OFF, test for B+ between the generator B+ output terminal (stud) to ground.

• If less than the specified range, test the circuit for a short to ground, an open or a high resistance.

2. Ignition OFF, disconnect the harness connector at the generator.
3. Ignition ON, test for greater than 3.5 V between the charge indicator control 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.

4. If the circuit test normal, replace the generator.

Repair Instructions

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

* Generator Replacement (V6) (Generator Replacement)Generator Replacement (V8) (Generator Replacement)Generator Replacement (LMM) (Generator Replacement)Generator Replacement (LGH) (Generator Replacement)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming