Knock Sensor: Testing and Inspection
Detonation "Knock" Sensor Circuit:
To test the Detonation Sensor and circuit, proceed as follows:
COMPONENT TEST
Testing of the detonation sensor is best done with a Digital Storage Oscilloscope (DSO)/Lab Scope.
1. Start and warm the engine to operating temperature.
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.
4. 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. If the harness test is OK, replace the sensor.
OSCILLOSC0PE TEST
1. Connect the pick-up lead of an oscilloscope to the #1 terminal of the sensor harness as shown in the image. Use the back-probing method or a break out box
2. Set the DSO for 2 volts per division and 50 milliseconds per division. Start the engine and warm to operating temperature.
Component Test:
3. 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.
Oscilloscope Display:
4. Operate the engine at 5000 rpm and observe the scope pattern.
5. If the pattern does not appear similar to the example, check the harness and replace the sensor if the harness checks O.K..
HARNESS TEST
1. Disconnect the ECM and detonation sensor connectors.
2. Using a Ohmmeter, check the continuity between the sensor harness terminal 1 and ECM harness connector terminal 58.
Continuity
Should exist
3. Using a Ohmmeter, check the continuity between the ECM harness terminal 58 and ground.
Continuity
Should not exist
4. Using a Ohmmeter, check the continuity between the sensor harness terminal 1 and ground.
Continuity
Should not exist
5. Using an ohm meter, check for continuity between the sensor harness terminal 2 and ground.
Continuity
Should exist
If any of the previous tests produce unsatisfactory results, the harness will need to be repaired or replaced. Once repairs have been completed, clear the trouble codes and road test the vehicle to confirm that the repair has corrected the problem and the code doesn't return.
If the same trouble code reoccurs, it is possible that there is an intermittent failure of the component or the ECM. Check for looseness at all harness junctions and test for an intermittent failure.