Knock Sensor: Description and Operation

GF07.04-P-6030AMG Component Description For A Knock Sensor







Knock sensor 1 is located on the right on the crankcase. It is protected against any strong effect of heat by a shield (removed in the picture).







Knock sensor 2 is located on the left on the crankcase. It is protected against any strong effect of heat by a shield (removed in the picture).

Task
The knock sensors detect vibrations for the purposes of knock control (combustion knocking) on the crankcase.

Knock sensor signals can also indicate engine damage (e.g. increased engine noise due to widened piston grooves).







Function
Vibrations on the crankcase are converted by piezocrystals inside the knock sensors into electrical voltage signals (about 0.13 to 4.7 V). These signals are transmitted over a 2-pin screened line to the ME control unit (N3/10).

Piezo-electric effect: An electrical voltage is generated by the mechanical force on a piezo crystal.