EGR Valve Position Sensor: Description and Operation

Positive Crankcase Ventilation And EGR Systems:

The function of the exhaust gas recirculation (EGR) system is monitored by the injection control unit. While the EGR valve is operated by vacuum, the vacuum supply is controlled by the EGR frequency valve, which is controlled by the ECU. This allows for a more precise control of when exhaust gasses are introduced into the combustion process, thus minimizing the affect on driveability and performance.

EGR FREQUENCY VALVE
The frequency valve is mounted in either of two locations, on top of the vacuum reservoir or cylinder head. The normal duty cycle of the frequency valve is 32% +/- 10% at 2000 RPM.

EGR TEMPERATURE SENSOR
Mounted to the side of the EGR valve.