Generator F Terminal

The F-terminal circuit connects the generator to the PCM. The PCM uses this circuit to monitor the Pulse Width Modulation (PWM) of the field circuit. When the key is in the RUN position and the engine is OFF, the PCM should detect a duty cycle near 0 percent. However, when the engine is running, the duty cycle should be between 5 percent and 100 percent.

The PCM monitors the PWM signal using a key ON test and a RUN test. During each test, if the PCM detects an out of range PWM signal, DTC P0622 will set. When the DTC sets, the PCM will send a Class 2 serial data message to illuminate the appropriate telltales.