Knock Sensor: Inspection

INSPECT KNOCK SENSOR

Measure the resistance of the sensor.

Standard resistance: 120 to 280 kΩ at 20°C (68°F)

If the result is not as specified, replace the knock sensor.

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.

Fig 1: Measuring Resistance Of Knock Sensor

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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.

DTC DETECTION CONDITION CHART

DTC No.	DTC Detection Condition	Trouble Area
P0327	Output voltage of knock sensor 0.5 V or less (1 trip detection logic)	Short in knock sensor circuit Knock sensor ECM
P0328	Output voltage of knock sensor 4.5 V or more (1 trip detection logic)	Open in knock sensor circuit Knock sensor ECM

HINT:

When any of DTCs 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 OFF.

Reference: Inspection using an oscilloscope.

The correct waveform is shown.

WAVEFORM REFERENCE

Items	Contents
Terminals	KNK1 - EKNK
Equipment Settings	0.01 to 10 V/Division, 0.01 to 10 msec./Division
Conditions	Keep engine speed at 4,000 rpm with warm engine

Fig 2: Oscilloscope Waveform Graph