Circuit Description
WARNING: This page is about a different car, the 2004 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.
Each knock sensor is fitted to the right bank and left bank of the cylinder block to detect engine knocking. This sensor contains a piezoelectric element which generates a voltage when it becomes deformed. The piezoelectric element sends a signal to the ECM, when the cylinder block vibrates due to knocking. If engine knocking occurs, ignition timing is retarded to suppress it.
Reference: INSPECTION USING OSCILLOSCOPE
- With the engine racing (4,000 RPM), check the waveform between terminals KNK1, KNK2 of the ECM connector and the body ground.
HINT:
The correct waveform is as shown in the illustration.
- Spread the time on the horizontal axis, and confirm that a period of the wave is 0.141 msec. (Normal mode vibration frequency of knock sensor: 7.1 kHz).
HINT:
If the normal mode vibration frequency is not 7.1 kHz, the sensor is malfunctioning.