Knock Sensor: Testing and Inspection

CIRCUIT DESCRIPTION
The knock sensor is attached to the cylinder block and senses 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:

Troubleshooting Procedures:

TROUBLESHOOTING HINTS
1. The MIL is ON or the DTC is displayed on the HI-SCAN under the following condition;
- When the knock sensor signal is not detected though the engine is in the over load condition.
2. When knock sensor signal is abnormally low.

Harness Inspection Procedures:

SENSOR INSPECTION
1. Disconnect the knock sensor connector.
2. Measure resistance between the terminal 1 and 2.
Standard value : about 5 Mohm [at 20 °C (68 °F)]
3. If the resistance is continuous, replace the knock sensor.
Knock sensor : 16 - 28 Nm (160 - 250 kg.cm, 11.8 - 18.4 lb.ft)
4. Measure the capacitance between the terminal 1 & 2.
Standard value : 800 - 1600 pF