Knock sensor component description - GF07.04-P-6030V

ENGINE 272.942 in MODEL 171

ENGINE 272.963 in MODEL 171

Location

The knock sensors are located at the top of the crankcase under the intake manifold.

Fig 1: Identifying Knock Sensor 1, Right And Left Knock Sensor 2 - Engines 272.920/940/941/960/970

Courtesy of MERCEDES-BENZ USA

Task

The knock sensors detect combustion knocks at excessively high vibrations at the crankcase. Anti-knock control thereby corrects the ignition timing for each individual cylinder when the engine is warm.

Body

The knock sensors function according to the piezoceramic principle. The screened cables are connected directly to the knock sensors.

Fig 2: Identifying Knock Sensor Signal Pattern - Engines 272.920/940/941/960/970

Courtesy of MERCEDES-BENZ USA

Function

Any vibrations which occur are converted with the aid of the piezoceramic into electrical signals.

Piezo-electric effect: If a mechanical force acts on a crystal, electrical voltages are produced.

The noise signal is modulated to a DC voltage from 0.13 to 4.7 V for transmission to the ME control unit.

Knock sensor signals may also indicate engine damage, e.g. increased engine noise resulting from a widened piston groove.