EGR Control Solenoid: Description and Operation

To regulate EGR flow, an ECM controlled Electronic Vacuum Regulator Valve (EVRV) solenoid is used in the vacuum line. The ECM uses information from the following sensors to regulate the solenoid:

^ Coolant Temperature Sensor (CTS)
^ Throttle Position Sensor (TPS)
^ Distributor (rpm Signal)
^ MAP
^ BARO

The EVRV regulator uses "pulse width modulation". This means the ECM turns the solenoid "ON" and "OFF" many times a second and varies the amount of "ON" time ("pulse width") to vary the amount of EGR.