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 | -- | -- |
Turn On Signal | P0621*, P2500** | -- | P0621*, P2501** | -- |
* 2.2L (L61) and 2.4L (LE5) engines only ** 2.0L (LNF) turbocharged engine only | ||||
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 sends a voltage signal to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. The ECM monitors the state of the generator turn ON signal circuit. The ECM should detect low voltage on generator turn on signal circuit when the ignition is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM should detect high voltage on the generator turn on signal circuit.
Conditions for Running the DTC
| • | The engine is running. |
| • | No generator, CKP sensors, CMP sensor DTCs are set. |
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. |
| • | The ECM will not illuminate the malfunction indicator lamp (MIL). |
| • | The ECM will store conditions, which were present when the DTC set as Fail Records data only. |
Conditions for Clearing the DTC
| • | A current DTC will clear 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
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
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, command the L-Terminal ON to 85% with a scan tool. Test for greater than 3 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. |
