Circuit/System Description

The EGR valve is controlled by the engine control module (ECM). The ECM controls the EGR valve by supplying a 12-volt pulse width modulated (PWM) signal to the EGR solenoid low control circuit and 12 volts to the high control circuit. The ECM monitors the difference between the desired mass air flow (MAF) and the actual MAF over a calibrated sampling time. If the average difference between desired and actual MAF during the specified time period is less than or greater than a calibrated threshold level the response time of detected EGR flow is determined to be out of range and a DTC will set.