B1492

DTC B1492

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 B1492
^ Generator F-Terminal Circuit Low

Diagnostic Fault Information





Circuit/System Description

The generator battery control module (GBCM) monitors the generator through the generator field duty cycle signal circuit. The signal is a 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 field duty cycle signal circuit is in the 0-5 percent range or pulled low to ground, then DTC B1492 will set.

Conditions for Running the DTC

* Vehicle in RUN mode and Engine Run Flag is True.
* The engine speed is less that 1,000 RPM.
* DTC B1487 or B1488 is not set as a current DTC.
* This diagnostic shall be run every 100 ms.

Conditions for Setting the DTC

The generator field duty cycle 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 turns ON.
* The driver information center (DIC) displays the BATTERY message.

Conditions for Clearing the DTC

The generator field duty cycle signal circuit input is greater than 5 percent duty cycle.

Diagnostic Aids

You must cycle the ignition after clearing the DTC to turn OFF the BATTERY DIC message.

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 Verification

With the scan tool installed, ignition ON and the Engine running, observe the scan tool ECM GEN-F Terminal Signal parameter. The parameter should read between 5 and 95 percent.

Circuit/System Testing

1. Ignition OFF, disconnect the generator and GBCM harness connectors.
2. Ignition ON and engine OFF, connect a test lamp to B+ and repeatedly probe the generator field duty cycle circuit X1 - 2, harness side while monitoring the GEN-F Terminal Signal Parameter. It should change from 0 percent to above 95 percent.

• If the parameter was not affected by the test lamp, test the circuit for a short to voltage, short to ground, or an open/high resistance.

3. If the circuit tests normal, replace the GBCM

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))