EGR System Operation
The EGR system is electronically controlled by the ECM and consists of an EGR solenoid, EGR valve, exhaust pressure regulator (EPR) solenoid, EPR valve, EGR vent solenoid valve, and vacuum pump.
The vacuum pump provides the system with vacuum for operation of the valves. The EGR and EPR solenoids are mounted at top rear of engine as an assembly.
The ECM controls the EGR solenoid to regulate the amount of vacuum at the EGR valve. The ECM controls the on-off time (duty cycle) of the EGR solenoid to regulate EGR flow.
By monitoring the data sensors, the ECM can calculate the required amount of EGR flow. When EGR flow should not be recirculated back into the engine, the ECM activates the EGR vent solenoid to rapidly vent vacuum from the EGR system.
During idle situations, the ECM energizes (closes) the EPR solenoid to increase exhaust backpressure. Increasing backpressure increases the EGR flow to help reduce emissions during idle.