Vauxhall Workshop Service and Repair Manuals

Knock Sensor  

Measurement:	Plot of voltage at the signal output of the knock sensor.
Check Objective:	Operational check

Preparation  

Switch off the engine and ignition.  

Connections  

INPUT A	COM/TRIGGER
Connect the red measurement lead to pin 1 (A) of the plug connector to the knock sensor. Connect the ground lead to pin 2 (B).

Procedure  

Use a metal object (hammer) to strike the engine block in the vicinity of the knock sensor. Regardless of the engine type and accessibility the following areas are particularly suitable. Below the bolt used to fasten the alternator to the engine block, flat surfaces on the engine block at the front or rear and the engine mounting (use extension if necessary).  

Reference Curve

The signal frequency of the knock sensors depends on various criteria and as a result cannot be used to assess the operation of the sensor.  

It can be assumed the above sensor is in good working order if when activated it generates a signal plot which simulates an attenuated oscillation.  

The amplitude (vertical deflection of the signal plot) is directly dependant on the impact magnitude and can likewise vary within broad limits.