Knock Sensor: Description and Operation

PURPOSE/OPERATION
The knock sensor converts knocking vibrations into electric signals. The signals are used by the engine control module to control ignition timing and turbo boost pressure. When engine knocking occurs, the crystal shakes and produces an A/C voltage signal. When engine knocking is detected by the engine control module, it retards the timing (maximum of 12° at the crankshaft) and reduces boost pressure (via the wastegate solenoid) to reduce the incidence. Some reduction in engine power will be noticed with the reduction in timing and boost.