Knock Sensor: Testing and Inspection

KNOCK SENSOR (KS)




The knock sensor is attached to the cylinder block and sense engine knocking conditions.

A knocking vibration from the cylinder block is applied as pressure to the piezoelectric element. This vibrational pressure is then converted into a voltage signal which is delivered as output. If engine knocking occurs, ignition timing is retarded to suppress it.

CIRCUIT DIAGRAM





HARNESS INSPECTION PROCEDURE





SENSOR INSPECTION
1. Disconnect the knock sensor connector.





2. Measure resistance between the terminal 2 and 3.

Standard value [at 20°C (68°F)]: about 5 MOhms

3. If the resistance is continual, replace the knock sensor.

Tightening torque: 16 - 28 Nm (160 - 250 kg.cm, 11.8 - 18.4 lb.ft)

4. Measure the capacitance between the terminal 2 & 3.

Standard value: 800 - 1600 pF


TROUBLESHOOTING PROCEDURES




MALFUNCTION SYMPTOM
When knock sensor signal is abnormally low.