EGR Control Solenoid: Description and Operation

To regulate EGR flow, an Engine Control Module (ECM) controlled Exhaust Gas Recirculation Electronic Vacuum Regulator solenoid is used in the vacuum line. The ECM uses information from the following sensors to regulate the solenoid:
- Engine Coolant Temperature
- Throttle Position Sensor
- Distributor (rpm signal)
The EGR vacuum control has an Exhaust Gas Recirculation Electronic Vacuum Regulator solenoid that 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.