Circuit/System Description
WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The exhaust gas recirculation (EGR) valve is controlled by the engine control module (ECM). The ECM controls the EGR valve by suppling a 12-volt pulse width modulated (PWM) signal to the EGR solenoid high control circuit and a ground to the low control circuit. The ECM monitors the EGR flow efficiency when the EGR is active by comparing the desired Mass Air Flow (MAF) to the actual MAF. If the actual MAF is less than or greater than a calibrated threshold level the amount of detected EGR flow is out of range.