B1492

DTC B1492

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* 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.


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 after completing the diagnostic procedure. Verification Tests

* Generator Replacement (With 4.2L Engine) Generator Replacement (With V8 Engine)