EGR Control Solenoid: Description and Operation

The EGR vacuum switching valve (VSV) is normally closed to prevent the EGR valve from opening when the engine is cold. The ECM will energize the VSV, allowing vacuum to operate the EGR valve, only when these conditions exist simultaneously:

1. Engine is at operating temperature.
2. Throttle position sensor is in "Off Idle" position.
3. Engine speed is above 1000 rpm.
4. MAP sensor indicates the engine is under load.