Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC P0621: Generator L-Terminal CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
B+ | P0622 | P0622 | -- | -- |
Field Duty Cycle Signal | P0622 | P0622 | -- | -- |
Charge Indicator Signal | P0621 | -- | P0621 | -- |
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
Connector End View Reference
Description and Operation
Charging System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the X1 harness connector at the generator.
- Ignition ON, test for less than 1 V between the signal circuit terminal 1 and ground.
- Engine running, test for greater than 3.5 V between the signal circuit terminal 1 and ground.
- If all circuits test normal, test or replace the generator.
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming. |
