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 | -- | P0621 | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine running. Parameter Normal Value: OK | |||
Turn On Signal | Fault | OK | Not Run |
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine running. Parameter Normal Value: OK | |||
Turn On Signal | Not Run | OK | Fault |
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. 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.
Conditions for Setting the DTC
The ECM detects low voltage on the generator turn on signal circuit 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 passes when condition for setting the DTC is no longer present. |
| • | The charge indicator and DIC message turn OFF when the DTC passes. |
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 Verification
Engine running, observing the following scan tool ECM circuit status parameters.
| • | GEN L-Terminal Ckt Short Gnd Test Status |
| • | GEN L-Terminal Ckt Short Volts Test Status |
The reading for each parameter should be OK.
Circuit/System Testing
- Ignition OFF, disconnect the X1 harness connector at the generator.
- Ignition ON, test for less than 1 V between the generator turn on signal circuit terminal 1 and ground.
- Engine Running, command the GEN-L Terminal circuit ON to 85% with a scan tool. 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. |
