Knock Sensor: Description and Operation

To control engine knock (detonation) at higher boost pressures, the turbocharging system utilizes a knock sensor and knock control unit.

The knock sensor, installed in the right rear side of the engine block, detects knocking and sends a signal to the knock control unit. The unit in turn signals the ECU that knock is occuring.

The ECU regulates boost pressure through its control of the wastegate solenoid valve. When knock occurs, the ECU energizes the solenoid valve to open the turbo wastegate, thus lowering boost pressure until knock is eliminated.

To further control knock, the ECU controlled Electronic Spark Advance (ESA) Control System will retard ignition timing 6° when the ECU receives a knock signal.

The system includes a warning buzzer to indicate possible faults with the wastegate, actuator or wastegate solenoid valve. If the buzzer sounds, these components should be checked.