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 B1487: Generator L-Terminal Circuit LowDiagnostic 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 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 when the engine is running is 5-100 percent.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The generator turn on signal is less than 5 percent duty cycle for 2 minutes.
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 greater than 5 percent duty cycle. |
| • | The charge indicator and SERVICE CHARGSYS message will remain ON until the ignition switch is cycled after the DTC is cleared. |
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. |
