Monitor Conditions

The PCM performs two diagnostic procedures to test the rationality of the EGR sensor signal: a position rationality test and a zero reference test. The position rationality test is performed continuously when the EGR control circuit is active. The zero reference test is performed when the valve is closed, with the throttle closed and engine RPM below a calibrated threshold, when the PCM is attempting to learn the position of the EGR valve during the closed valve state.