Wastegate Solenoid: Description and Operation

Wastegate Solenoid Valve Location:

The wastegate solenoid valve is used to regulate the turbocharger maximum boost pressure in the event of a air flow or detonation sensor failure. The ECU uses vehicle load condition inputs from the detonation sensor and the air flow sensor to regulate the amount of manifold pressure or vacuum to the solenoid. The wastegate solenoid is spring loaded in the closed (lowest boost) position until after the engine is started. After engine start, under normal conditions, the ECU will open the solenoid valve by fully grounding the circuit (highest boost) and leave it grounded while the engine is running. This allows some of the boost pressure, that would normally operate the wastegate actuator, to be bled off. This supplies the wastegate actuator diaphragm with an artificially low reading of intake boost pressure. Because of the way the actuator works (boost pressure balanced against a preset spring pressure), this causes the actuator to allow a higher pressure. Once the ECU determines that a failure has occurred, it interrupts the ground allowing the solenoid valve to close. This causes full boost pressure to by applied to the wastegate actuator diaphragm. With full boost applied the actuator overcomes the spring at a lower boost pressure.