The generator battery control module (GBCM) controls the generator through the generator turn on signal circuit, or L-terminal circuit. The signal is a 5-volt pulse width modulation (PWM) signal of 128 Hz, and the GBCM varies the duty cycle. Normal duty cycle is between 5-95 percent when the engine is running. If the generator turn on signal circuit is 95 percent or greater duty cycle or pulled high to voltage, then DTC B1488 will set.

The generator turn on signal circuit is greater than 95 percent for 5 seconds.

The DTC will pass when the generator turn on signal circuit is less than 95 percent for 5 seconds.

Schematic Reference

Starting and Charging Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Charging System Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF, disconnect the harness connector at the generator.
2. Ignition ON, test for less than 1 volt between the generator turn on signal circuit terminal 1 X1 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.

3. Engine running, test for greater than 3.5 volts between the generator turn on signal circuit terminal 1 X1 and ground.

⇒	If less than the specified range, test the generator turn on signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the GBCM.

4. If the circuit tests normal, replace the generator.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.