Circuit Description

A flat type knock sensor (non-resonant type) has a structure that can detect vibrations over a wide band of frequencies: between approximately 6 kHz and 15 kHz.

Knock sensors are fitted onto the engine block to detect engine knocking.

The knock sensor contains a piezoelectric element which generates a voltage when it becomes deformed.

The voltage is generated when the engine block vibrates due to knocking. Any occurrence of engine knocking can be suppressed by delaying the ignition timing.

Fig 1: DTC Trouble Detection Chart (DTC P0325/0327/0328)

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

HINT:

When any of DTCs P0325, P0327 and P0328 are set, the ECM enters fail-safe mode. During fail-safe mode, the ignition timing is delayed to its maximum retardation. Fail-safe mode continues until the ignition switch is turned to OFF.

Fig 2: View Of KNK 1 Signal Waveform

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Reference: Inspection using an oscilloscope.

The correct waveform is shown.