P0621

DTC P0621

Diagnostic Instructions

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

DTC Descriptor
DTC P0621
- Generator L-Terminal Circuit

Diagnostic Fault Information





Typical Scan Tool Data













Circuit/System Description

The engine control module (ECM) uses the generator turn on signal circuit, or L-terminal circuit, to control the load of the generator on the engine. A high side driver in the ECM applies a voltage to the voltage regulator.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The ECM detects high or low voltage on the generator turn on signal circuit for 15 seconds.

Action Taken When the DTC Sets

The charge indicator turns ON.

Conditions for Clearing the DTC

* The DTC will pass when the conditions for setting the DTC are no longer met for 1 second.
* 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 Verification

Engine running, observe the following scan tool ECM control circuit status parameters.

* GEN L-Terminal Ckt Short Gnd Test Status
* GEN L-Terminal Ckt Open Test Status
* GEN L-Terminal Ckt Short Volts Test Status

Each parameter should read OK or Not Run.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the generator.
2. Engine running, command the GEN L-Terminal ON with a scan tool. 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, an open or a high resistance. If the circuit tests normal, replace the ECM.

3. If the circuit tests normal, test or replace the generator.

Repair Instructions

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

* Generator Replacement (LE5) (Generator Replacement)Generator Replacement (LY7) (Generator Replacement)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming.