Laser FWD L4-1997cc 2.0L DOHC Turbo (1993)
Detonation (Knock) Sensor: Testing and Inspection
Component Test
Detonation (Knock) Sensor Circuit
COMPONENT TEST
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, next to the sensor.
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.
2. Start the engine and warm to operating temperature.
Oscilloscope Display
3. Operate the engine at 5000 rpm and observe the scope pattern.
4. If the pattern does not appear similar to the example, check the harness and replace the sensor if the harness checks OK.
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.
