B1487

DTC B1487

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

DTC Descriptor
DTC B1487
- Generator L-Terminal Circuit Low

Diagnostic Fault Information





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 ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Charging System Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the generator.
2. 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.

• 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.

3. 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 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.

4. If the circuit tests normal, replace the generator.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Generator Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for GBCM replacement, setup, and programming.