Exhaust Gas Recirculation (EGR) System Description: Operation

The PCM uses the inputs from various sensors in order to control the operation of the EGR valve. Information from the engine coolant temperature (ECT) sensor, the throttle position (TP) sensor, the vehicle speed sensor (VSS), and the manifold absolute pressure (MAP) sensor are critical for proper EGR valve operation. Under heavy engine loads, when the demand for power is high, the EGR valve is closed. In order to insure a smooth idle and stable engine operation, the EGR valve is also closed at closed throttle engine operation. The EGR valve is usually open during low and medium engine loads and speeds. Combining pre-programmed engine calibrations with various sensor inputs, the PCM calculates the optimum opening of the EGR valve.