P0621

DTC P0621

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 Descriptors
DTC P0621 58
- Generator L-Terminal Circuit Performance

DTC P0621 59
- Generator L-Terminal Circuit Protection Time-Out

Diagnostic Fault Information





Circuit/System Description

The generator battery control module (GBCM) controls the generator through the turn on control circuit, or L-Terminal circuit. The control is a 5 V pulse width modulation (PWM) signal of 128 hz. Normal duty cycle when the engine is running is 5-100 percent.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The generator turn on control is less than 5 percent duty cycle for 2 minutes.

Action Taken When the DTC Sets

* The charge indicator turns ON.
* The driver information center (DIC) displays the SERVICE CHARGSYS message.

Conditions for Clearing the DTC

* The DTC will pass when the generator turn on control is greater than 5 percent duty cycle.
* The charge indicator and SERVICE CHARGSYS message will remain ON until the ignition switch is cycled after the DTC is cleared.

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 (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

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

Circuit/System Testing

1. Verify that a test lamp illuminates between the generator B+ terminal AX2 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

2. Ignition OFF, disconnect the X1 harness connector at the generator.
3. Ignition ON, test for less than 1 V between the control circuit terminal 1 and ground.

• If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the GBCM.

4. Engine running, test for greater than 3 V between the control circuit terminal 1 and ground.

• If less than the specified range, test the control circuit for a short to ground, or an open/high resistance. If the circuit tests normal, replace the GBCM.

5. If all circuits test normal, test or replace the generator.

Repair Instructions

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

* Generator Replacement (LLR) (Service and Repair)Generator Replacement (LH8) (Service and Repair)
* Control Module References (Programming and Relearning)for GBCM replacement, setup, and programming