Knock Sensor, Basic Function - GF07.04-P-2001A

Engine 139, 176, 177, 254, 256, 260, 264, 274, 279, 282 

Engine 177, 256 

Example illustration of knock sensor 

Overview 

This document contains information on:

• General 
• Function 

General 

The knock sensors (1.1, 1.2) detect, in each case, the vibrations at the crankcase that arise during the combustion in the individual cylinders.

The knock sensors (1.1, 1.2) transmit the detected vibrations as voltage pulses to the combustion engine control unit.

Example of knock sensor signal 

Courtesy of MERCEDES-BENZ USA

Function 

The knock sensors (1.1, 1.2) basically consist of a moving seismic mass and a layer of solid piezo crystals.

The vibrations at the crankcase are transmitted via an inertia mass to an inner piezoelement and are converted into electrical voltage pulses.

If the extraordinary vibrations that arise due to the knocking combustion occur at the crankcase, these are adapted by the seismic mass in the knock sensors (1.1, 1.2). The striking of the seismic mass impact against the piezo crystals generates a voltage signal which can be detected by the combustion engine control unit.

As a result, the firing point is retarded until no knocking noises whatsoever are registered by the knock sensors (1.1, 1.2). Via the knock control with knock sensors (1.1, 1.2), the combustion engine is permanently kept close to the so-called knock limit and the engine output is optimized.

	Detailed information
	Knock sensor, detailed information	Engine 254 in model 236 Engine 256 in model 214, 236 Engine 260, 282 in model 118 up to model year 2023 Engine 260, 282 in model 177, 247 up to model year 2022 Engine 264 in model 167	GF07.04-P-2501A
		Engine 139 in model 118 up to model year 2023 Engine 139 in model 177, 247 up to model year 2022 Engine 139 in model 206, 236	GF07.04-P-2501C
	Component descriptions
	Knock sensor, component description	Engine 176, 177, 256, 279 in model 223	GF07.04-P-6030A
		Engine 139, 254 in model 206	GF07.04-P-6030C
		Engine 139, 177 in model 232	GF07.04-P-6030F
		Engine 139, 254 in model 254	GF07.04-P-6030H
		Engine 254, 256 in model 214	GF07.04-P-6030K
		Engine 139, 260, 282 in model 118 as of model year 2023	GF07.04-P-6030L
		Engine 139, 260, 282 in model 177, 247 as of model year 2022 Engine 176, 177, 254, 256, 264, 274 in model 167 as of model year 2023	GF07.04-P-6030M
		Engine 139, 177 in model 192	GF07.04-P-6030R
		Engine 177, 254, 256 in model 236	GF07.04-P-6030S
		Engine 177.8 in model 465.2 Engine 256.8 in model 465.2	GF07.04-P-6030T