Knock sensor detect knock or ping in the motor, which is pre detonation and can cause serious and expensive damage to the motor. If knock is detected the sensor will tell the management system of the engine to severely retard the ignition. Besides an error code you will notice a lack of power and throttle response.Here I share the procedures of how to replace Benz knock sensor.
The sensors are easy to replace once you get access to them. Unfortunately, you will need to remove the fuel rail, injectors and intake manifold. Please see our articles on how to perform this work. Note: The knock sensors are torque sensitive and over or under torquing them will result in incorrect readings from the sensors and poor performance from the motor. The sensors must be torqued to 20Nm on the 272 engine.
Applies to: C350 (2007-14), SLK350 (2004-14), CLS350 (2004-14), CLK350 (2005-14), E350 (2005-14), S350 (2005-14), SL350 (2005-14), R350 (2006-14), ML350 (2006-14), Viano (2005-14), Sprinter (2006-14), CLC350 (2008-14), GLK350 (2008-12)
Time: 30 minutes
Tab: $35 to $70
Talent: 2 T
ools: E10 socket, torque wrench
Parts Required: New knock sensors sensor, intake manifold gasket
Hot Tip: Don’t work on a hot engine
Performance Gain: Piece of mind on engine knock
Complementary Modification: New injectors
You need to remove the engine covers and air intake ducts to perform this work,check here to get the detail information: How to Remove Benz C Class W204 Engine Cover
Next you need to remove the intake manifold to get the motor to this stage.Please see our article on intake manifold removal:How to Remove Mercedes Benz Intake Manifold
With the manifold removed you can see the two knock sensors in the “V” of the motor (red arrow).There is one knock sensor for each bank of cylinders.
The clips used to hold the wiring connection to the sensors is quite beefy,squeeze in both side of the clips and wiggle the connection off (red arrows)
Use an E10 socket and remove the old sensor (red arrow)
The knock sensors are torque sensitive and over or under torqueing them will result in incorrect readings from the sensors and poor performance from the motor.The sensors must be torqued to 20Nm on the 272 engine.