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





Typical Scan Tool Data





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

The engine is running.

Conditions for Setting the DTC

The generator field duty cycle 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 BATTERY NOT CHARGING message.

Conditions for Clearing the DTC

* The DTC will pass when the generator field duty cycle signal circuit has greater than 5 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 Verification

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 terminal 2 X1, harness side while monitoring the scan tool ECM GEN-F Terminal Signal parameter. The parameter should change from 0 percent to greater than 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.

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