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. 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 is between 5-95 percent. If the generator turn on signal circuit is in the 0-5 percent range, pulled low to ground or open then DTC B1487 will set.

Conditions for Running the DTC

* The engine speed is greater than 450 RPM.
* This diagnostic shall be run every 100 ms.

Conditions for Setting the DTC

The generator turn on signal circuit is less than or equal to 5 percent duty cycle for more than 120 seconds.

Action Taken When the DTC Sets

* The charge indicator illuminates on the instrument panel cluster (IPC).
* The driver information center (DIC) displays the BATTERY message.

Conditions for Clearing the DTC

The generator turn on signal circuit input is from 5-95 percent duty cycle, greater than 0 volts.

Reference Information

Schematic Reference

Starting and Charging Schematics ([1][2]Electrical Diagrams)

Connector End View Reference

Component Connector End Views (Component Connector End 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 (Control Module References) 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 X1 - 1 and ground.

• If less than the specified range, test the generator turn on signal circuit for a short to ground, an open or a 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 X1 - 1 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.

4. If the circuit tests normal during the ignition ON/Run test, replace the generator.

Repair Instructions

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

* Control Module References (Control Module References) for GBCM replacement, setup, and programming
* Generator Replacement (With 4.2L Engine) ()Generator Replacement (5.3L Engine) (Generator Replacement (5.3L Engine))