Circuit Description

WARNING: This page is about a different car, the 2002 Pontiac Sunfire and 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

PCM uses generator field duty cycle signal circuit to monitor duty cycle of generator. generator field duty cycle signal circuit connects to high side of field winding in generator. A Pulse-Width Modulated (PWM) high side driver in voltage regulator turns field winding ON and OFF. PCM uses PWM signal input to determine generator load on engine. This allows PCM to adjust idle speed to compensate for high electrical loads. PCM monitors state of generator field duty cycle signal circuit. When key is in RUN position and engine is OFF, PCM should detect a duty cycle near zero percent. However, when engine is running, duty cycle should be between 5 percent and 100 percent. PCM monitors PWM signal using a key ON test and a RUN test. During tests, if PCM detects an out of range PWM signal, DTC P0622 will set. When DTC sets, PCM will send a class 2 serial data message to IPC to illuminate charge indicator.