Circuit Description
WARNING: This page is about a different car, the 1995 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
EGR vacuum is regulated by an PCM-controlled, normally closed solenoid. PCM will turn EGR on and off (duty cycle) by grounding and ungrounding solenoid drive circuit. Duty cycle is calculated by PCM based on coolant temperature, airflow and engine RPM. PCM will check EGR operation when vehicle speed is 16-32 MPH, MAP is within calibrated range, throttle angle is zero percent and vehicle is coasting.