Circuit Description

The EGR valve is controlled by an ECM-operated solenoid. The solenoid is normally closed. The ECM provides a ground to energized the solenoid which allows vacuum to flow to the EGR valve.

The ECM monitor EGR effectiveness by de-energizing the EGR control solenoid, thereby shutting off vacuum to the EGR valve diaphragm. With the EGR valve closed, fuel integrator counts will be greater than they were during normal EGR operation. If the change is not within the "calibrated window", Code 32 will be set.

The ECM checks EGR operation when vehicle speed is over 50 MPH, engine vacuum is 11.8-51.1 in. Hg, and throttle position is constant (no change during check sequence).