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 ()

Connector End View Reference

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))