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 Descriptor
DTC P0621
- Generator L-Terminal Circuit

Diagnostic Fault Information





Circuit/System Description

The engine control module (ECM) uses the charge indicator signal circuit, or L-terminal circuit, to control the power output of the generator, and to control the load of the generator on the engine. A high side driver in the ECM supplies voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. The ECM monitors the state of the charge indicator signal circuit. The ECM should detect low voltage on the charge indicator signal circuit when the ignition is ON and the engine is OFF, or if the generator malfunctions. When the engine is running, the ECM should detect high voltage on the charge indicator signal circuit.

Conditions for Running the DTC

* The ignition is ON.
* No crankshaft or camshaft position sensor DTCs are set.

Conditions for Setting the DTC

One of the following conditions exist:

* The engine is OFF, and the signal circuit is shorted to voltage for 5 seconds.
* The engine is running, and the signal circuit is shorted to ground for 15 seconds.

Action Taken When the DTC Sets

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

Conditions for Clearing the DTC

* The DTC will pass when the conditions for setting the DTC are no longer met.
* A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

Reference Information
Schematic Reference

Starting and Charging Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
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. Ignition OFF, disconnect the X1 harness connector at the generator.
2. Ignition ON, test for less than 1 V between the signal circuit terminal 1 and ground.

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

3. Engine running, test for greater than 3.5 V between the signal circuit terminal 1 and ground.

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

4. 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 (Generator Replacement)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming.