B1487

DTC B1487

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) 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, and the GBCM varies the duty cycle. Normal duty cycle is between 5-95 percent when the engine is running. 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.

Conditions for Setting the DTC

The generator turn on signal circuit has 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 BATTERY NOT CHARGING message.

Conditions for Clearing the DTC

* The DTC will pass when the generator turn on signal circuit has 5-95 percent duty cycle.
* The charge indicator and DIC message will remain ON until the ignition is cycled after the DTC clears.

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 (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

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. Engine running, test for greater than 3.5 volts between the generator turn on signal circuit terminal 1 X1 and ground.

• 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.

3. Ignition ON, 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 signal circuit for a short to voltage. 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 (With 4.2L Engine) ()Generator Replacement (5.3L Engine) ()
* Control Module References (Programming and Relearning) for GBCM replacement, setup, and programming.