Circuit/System Description

The generator battery control module (GBCM) and the engine control module (ECM) monitor 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 5-99 percent. If the generator field duty cycle signal circuit is in the 0-5 percent range or pulled low to ground while the engine is running, then the GBCM will set DTC B1492.