Knock Sensor
The knock sensor is located on the engine block, cylinder head, or the intake manifold. This is because the function of this sensor is to sense vibrations an engine creates. The PCM uses this signal to alter the ignition timing and prevent detonation. It will compare this information with its preset tables to identify an engine knock or ping. If a ping is sensed it will retard the timing to protect the engine from this damaging pre-ignition.
The knock sensor is a piezoelectric sensor that contains a piezoelectric sensing crystal and a resister. This crystal creates a small amount of voltage when shaken. This sensor takes advantage of this property.
Symptoms: The symptoms of a bad knock sensor usually show up at highway speeds or under a load. Be clear that this sensor effects the ignition timing of an engine. The vehicle will have a loss in fuel mileage and acceleration especially at highway speeds. The customer may complain that the vehicle doesn't feel right. The vehicles computer will detect a bad knock sensor, set off a code (P0325-P0332), and enter failsafe mode.
