The EGRC-solenoid valve repsonds to singals from the ECM. When the ECM snes an ON signale, the coild in the solenoid valve is energized. A plunger will then ove to tcut the vacuum signal from the throttle body ot the EGR valve. When the ECM sends an OFF signal, the cavuum signal passes through the solenoid valve. The signal thenreaches the EGR valve.