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 started cold and blocks the vacuum signal to protect the EGR valve diaphragm from excess turbocharger pressure. The ECM will energize the VSV and allow EGR valve operation only when preprogrammed values from these devices are met:

Coolant temperature sensor
MAP sensor
Throttle position sensor
Engine rpm