Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | 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 LowDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Generator Field Duty Cycle Signal | B1492 | B1492 | -- | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine running. Parameter Normal Range: 5 - 99% | |||
Generator Field Duty Cycle Signal | 0% | 0% | 99% |
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
Connector End View Reference
Description and Operation
Charging System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References 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
- Ignition OFF, disconnect the generator and GBCM harness connectors.
- 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 circuit tests normal, replace the GBCM
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for GBCM replacement, setup, and programming. |
