Knock Sensors

WARNING: This page is about a different car, the 2018 Land Rover Discovery Sport. However, it is still accessible from the selected car via links, so may be relevant.

ITEM	DESCRIPTION
1	Knock sensor - Front
2	Knock sensor - Rear

The knock sensors are piezo-ceramic sensors. The knock sensors allow the Powertrain Control Module (PCM) to employ active knock control and prevent engine damage from pre-ignition or detonation.

Each knock sensor is secured with a single screw. On each knock sensor, a two pin electrical connector provides the interface with the engine harness.

The PCM compares the signals from the knock sensors with preset tables in its memory to determine when detonation occurs. When detonation is detected, the PCM retards the ignition timing on that cylinder and then gradually returns it to the original setting.

The PCM cancels closed loop control of the ignition system if the signal received from a knock sensor becomes implausible. In these circumstances the PCM defaults to base mapping for the ignition timing. This provides the engine will not become damaged if low quality fuel is used. The Malfunction Indicator Lamp (MIL) will not illuminate, although the driver may notice that the engine 'knocks' in some driving conditions. The 'knocks' displays a drop in performance and smoothness.

The PCM calculates the default value if a sensor fails.