Electronic EGR Control Operation

EGR system is electronically controlled by the ECM and consists of an EGR solenoid, EGR valve, EPR solenoid, EPR valve and vacuum pump. The vacuum pump provides the system with vacuum to operate valves. The EGR and EPR solenoids are mounted at top rear of engine as an assembly.

ECM controls on and off time (duty cycle) of the EGR solenoid. This regulates amount of EGR flow into engine by controlling vacuum applied to EGR valve. The ECM calculates the amount of EGR flow required based on information supplied by following input sensors: Engine RPM, EGR control vacuum, barometric pressure, vehicle speed and metering valve position.

A Quick Vacuum Response (QVR) valve is located in vacuum line between EGR solenoid and valve, and in vacuum line between EPR solenoid and valve. Its purpose is to quicken response time when opening and closing EGR and EPR valves.