Generator Circuit Diagnosis (F Terminal)

Electrical Diagram:

CIRCUIT DESCRIPTION

The F terminal circuit from the generator is a pulse width modulation (PWM) signal to the PCM. The PCM detects the PWM frequency by sampling the average voltage at the F terminal of the generator. When the ignition switch supplies ignition 1 voltage, the generator goes to a predetermined duty cycle. When the generator is up and running, the generator regulator starts regulating and suppling the current. Therefore, with no failures with the vehicle's charging system, the field terminal circuit voltage will be at a low value and stay there until roughly 0.5 second after the engine idles. When the engine is idles, the voltage transitions to a higher value.

DIAGNOSTIC AIDS

A generator fault, such as a shorted output diode, malfunctioning regulator, an open or shorted rotor, or an open sense lead may cause a low battery charge. Refer to Engine/Engine Electrical for further information and generator diagnosis.