Exhaust Gas Recirculation: Description and Operation

PURPOSE
The Exhaust Gas Recirculation (EGR) system returns a small amount of exhaust gas into the intake manifold. This reduces the overall combustion temperature. Cooler combustion temperature provides a significant reduction of Oxides of Nitrogen (NOx).

OPERATION
The Powertrain Control Module (PCM) controls the EGR Vacuum Regulator (EGR-VR) Solenoid. The EGR-VR solenoid controls the vacuum to the EGR valve. When the EGR valve opens, exhaust gas flows to the intake manifold to be returned to the combustion cycle. The EGR backpressure transducer monitors the flow and returns a signal to the PCM.

The Amount of Recirculated Exhaust Gas Depends Upon:

- Engine RPM.

- Intake manifold vacuum.

- Exhaust back pressure.

- Engine coolant temperature.

- Throttle position.