Knock Control

Knock Sensor (R50)

Function
The knock sensor is a piezo-electric acceleration sensor. The sensor produces an output voltage proportional to the mechanical vibrations generated by the engine. The engine control module receives a signal, filters out the noise and then calculates whether the engine is knocking. The camshaft and the crankshaft provide the engine control module with position information. The engine control module can use this to calculate which cylinder is knocking. The ignition for this cylinder is set to late as far as is necessary to stop the knocking. This only takes place within the limit values. The engine control module then adjusts the ignition to early until the optimum firing point for this cylinder under these conditions is reached.

Installation Location
The knock sensor is located on the intake end of the engine block.

Failure
If the knock sensor fails, the engine control module is unable to detect and correct knocking. The engine then knocks. The performance of the engine is reduced and the fuel consumption is influenced. Standard values are used for the ignition timing. A fault code is written to the engine control module.