Knock Sensor

Fig 21 Knock Sensor:

When the knock sensor detects a knock in one of the cylinders, it sends an input signal to the PCM. In response, the PCM retards ignition timing for all cylinders by a scheduled amount.

Knock sensors contain a piezoelectric material which sends an input voltage (signal) to the PCM.
- As the intensity of the engine knock vibration increases, the knock sensor output voltage also increases.

The knock sensor threads into the side of the cylinder block in front of the starter (Fig. 21).