Closed loop diesel engine EGR control including event monitoring

A control system and method for an EGR valve (54), particularly in a diesel engine (30). A processor processes data in feedback control of the position of the valve element to develop from the data a position control signal for setting the extent to which the valve is open. The processing includes processing data (EGRP) corresponding to actual position of the valve and data (EGRP_DES) representing a desired position of the valve to develop a position error signal (EGRP_ERR), processing data (EGR_RATE_FDBK) that defines actual EGR rate and data (EGR_RATE-DES) representing a desired EGR rate to develop a rate error signal (EGR_RATE_ERR), and processing the position error signal (EGRP_ERR) and the rate error signal (EGR_RATE_ERR) to develop the position control signal (EGRP_DTY). Emission control system event monitors (200, 202) flag potential error sources in their incipiency to afford opportunity for correction before mandatory logging occurs.