Knock Sensor: Testing and Inspection

System Schematic:

The following steps are used to test the operating of the detonation sensor system.
1. The engine must be at normal operating temperature and idling.
2. Connect a timing light to the engine cyl #1 and check the timing marks.
3. While watching the timing marks, lightly tap on the cylinder block with a hammer or wrench, next to the sensor.
While tapping on the block the timing should be seen to retard and advance approximately 8° in conjunction with the tapping. If the timing does not change, then the harness should be tested and checked for continuity or bad connections between the igniter and the sensor. If the harness test is OK, replace the sensor.


SENSOR TEST

Testing of the detonation sensor is best done with a Digital Storage Oscilloscope (DSO)/Lab Scope.
To test the sensor, connect the probe from the scope to the sensor connector using the back-probing method or a break out box. Set the DSO for 2 volts per division and 50 milliseconds per division.

Component Test:

Tap lightly on the engine block next to the sensor with a hammer or wrench and observe the signal pattern. You should see a voltage spike and it should correspond to the intensity and timing of the tapping. If the pattern does not appear, then the harness should be tested and checked for continuity or bad connections between the igniter and the sensor. If the harness test is OK, replace the sensor.