C 3500 Truck 2WD V8-454 7.4L (1990)
Electronic Vacuum Regulator Valve (EVRV): Description and Operation
Electronic Vacuum Regulator Valve Solenoid (EVRV) Over 8500 Gvw
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
^ Throttle Position (TPS)
^ P/N switch
^ Distributor (rpm Signal)
The EGR vacuum control has an EVRV 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.
