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 |
|---|---|---|---|---|
Generator 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-volt pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle when the engine is running is between 5-100 percent. If the generator turn on signal circuit is in the 0-5 percent range, or pulled low to ground, then DTC B1487 will set.
Conditions for Running the DTC
| • | The engine is running. |
| • | This diagnostic shall run every 100 ms. |
Conditions for Setting the DTC
The generator turn on signal circuit 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 CHARGE SYS message. |
Conditions for Clearing the DTC
| • | The DTC will pass when the generator turn on signal circuit input is greater than 5 percent duty cycle. |
| • | The charge indicator and DIC 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 harness connector at the generator.
- Ignition ON, GEN L-Terminal Signal Command 0%, test for less than 1 volt between the generator turn on signal circuit terminal 1 X1 and ground.
- Command the GEN L-Terminal Signal ON to 80% duty cycle with a scan tool. Test for 3.0 volts between the generator turn on signal circuit terminal 1 X1 and ground.
- If the circuit tests normal, replace the generator.
| ⇒ | If greater than the specified range, test the generator turn on signal circuit for a short to voltage. If the circuit tests normal, replace the GBCM. |
| ⇒ | If less than the specified value, test the generator turn on 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. |
