For 1990-2009 cars only
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 B1488: Generator L-Terminal Circuit HighDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
B+ | B1492 | B1492 | -- | -- |
Field Duty Cycle Signal | B1492 | B1492 | -- | -- |
Turn On Signal | B1487 | -- | B1488 | -- |
Circuit/System Description
The generator battery control module (GBCM) controls the generator through the generator turn on signal circuit, or L-Terminal circuit. The signal is a 5 V pulse width modulation (PWM) signal of 128 Hz. Normal duty cycle is 0% when the engine is off.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The engine is OFF. |
Conditions for Setting the DTC
The generator turn on signal is greater than 65 percent duty cycle for 5 seconds.
Action Taken When the DTC Sets
| • | The charge indicator turns ON. |
| • | The driver information center (DIC) displays the SERVICE CHARGSYS message. |
Conditions for Clearing the DTC
| • | The DTC will pass when the generator turn on signal is less than 65 percent duty cycle for 5 seconds. |
| • | The charge indicator and SERVICE CHARGSYS 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
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, engine OFF, GEN L-Terminal Signal Command 0%, test for less than 1 V between the signal circuit terminal 1 and ground.
- Engine running, command the GEN L-Terminal Signal ON to 80% duty cycle 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 GBCM. |
| ⇒ | 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 GBCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for GBCM replacement, setup, and programming. |
