EGR Control Solenoid: Description and Operation

EGR Circuit - EVRV Solenoid:

PURPOSE
To provide electrical control of the Exhaust Gas Recirculation (EGR) valve.

OPERATION
The Engine Control Module (ECM) operates a Electronic Vacuum Regulator Valve (EVRV) solenoid to control the EGR valve. 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 modulation") to vary the amount of EGR.
The ECM uses RPM and information from the following sensors to regulate the EGR solenoid:
- Engine Coolant Temperature (ECT) sensor
- Throttle Position (TP) sensor
- Manifold Absolute Pressure (MAP) sensor
- Park/Neutral Position (PNP) switch
- Torque Converter Clutch (TCC)
- Vehicle Speed Sensor (VSS)

The ECM monitors EGR effectiveness by de-energizing the EGR control solenoid, thereby, shutting "OFF" vacuum to the EGR valve diaphragm. With the EGR valve closed, and O2S fluctuating normally, short term fuel trim counts will be greater than they were during normal EGR operation. If the change is not within the calibrated window, a DTC 32 will be set.
The ECM will check operation when:
- Vehicle speed is above 50 mph.
- Engine vacuum is between 12.5 and 55 kPa (1.8 and 7.4 psi).
- TP angle between 5% and 30%.
- All conditions met twice for 60 seconds.