Knock Sensor: Testing and Inspection

KNOCK SENSOR




The knock sensor is a piezoelectric device attached to the cylinder block that senses pressure from engine knocking conditions. This vibrational pressure is then converted into a voltage signal which is delivered as output. If engine knock occurs, ignition timing is retarded to suppress it.

Circuit Diagram:

Troubleshooting Procedures:

TROUBLESHOOTING HINTS

1. The MIL is ON or the DTC is displayed on the HI-SCAN PRO under the following condition:
- When the knock sensor signal is not detected, even though the engine is in an overload condition
- When the knock sensor signal is abnormally low.

Harness Inspection Procedures:

SENSOR INSPECTION

1. Disconnect the knock sensor connector.
2. Measure the resistance between terminals 1 and 2.

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

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

Knock sensor: 19.6 - 24.5 Nm (200 - 250 kg.cm, 14.5 - 18.1 lb.ft)




4. Measure the capacitance between the terminal 1 and 2

Standard value: 800 - 1600 pF