Exhaust Gas Recirculation: Description and Operation

The Exhaust Gas Recirculation (EGR) system recirculates exhaust gas to reduce combustion temperatures and NOx emissions. The amount of recirculation varies from zero with a cold engine to a fixed flow rate with an engine at normal operating temperature, intermediate load and low engine speed. The flow increases steadily as coolant temperature rises above 131°F (55°C). The system employs a control solenoid controlled by the PCM and sensor system. The PCM will disable the EGR system under conditions of zero throttle opening, full throttle, low coolant temperature, low engine speed, transmission in neutral, or system malfunction.