DTC 52

DTC 52 - Knock Sensor Signal




NOTE: If the ECM detects the above diagnosis conditions, it operates the fail safe function in which the corrective retard angle value is set to the maximum value.

CIRCUIT DESCRIPTION
Knock sensor is fitted the cylinder block to detect engine knocking. This sensor contains a piezoelectric element which generates a voltage when it becomes deformed, which occurs when the cylinder block vibrates due to knocking. If engine knocking occurs, ignition timing is retarded to suppress it.

DIAGNOSTIC TROUBLE CODE DETECTION DRIVING PATTERN
Purpose of the driving pattern:
- To simulate diagnostic trouble code detecting condition after diagnostic trouble code is recorded.
- To check that the malfunction is corrected when the repair is completed by confirming that diagnostic trouble code is no longer detected.

NOTE: If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.

Malfunction: Open or Short in Knock Sensor



1. Start engine and warm it up.
2. Idle the engine for 3 minutes.
3. With the A/C ON, quickly race the engine to 5,000 rpm 3 times.
- If a malfunction exists, the Malfunction Indicator Lamp will light up when the engine quickly raced.

WIRING DIAGRAM





INSPECTION PROCEDURE

















Inspection Using Oscilloscope

With the engine racing (4,000 rpm) measure waveform between terminal KNK of engine control module and body ground. The correct waveform is as shown.:

Spread the time on the horizontal axis, and confirm that the period of the wave is 123 microseconds (Normal mode vibration frequency of knock sensor: 8.1 KHz).:

HINT: If normal mode vibration frequency is not 8.1 KHz, the sensor is malfunctioning.