DTC 52

CIRCUIT DESCRIPTION
Knock sensors are fitted one each 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, which occurs when the cylinder block vibrates due to knocking. If engine knocking occurs, ignition timing is retarded to suppress it.
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.





DETECTING CONDITION AND TROUBLE AREA

DIAGNOSIS 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 confirming that diagnostic trouble code is no longer detected.

Malfunction: Open or Short in Knock Sensor:





1. Start engine and warm up.
2. Let the engine idle for 3 minutes.
3. With the A/C ON, quickly race the engine to 5,000 rpm 3 times. (Rapidly depress the accelerator pedal and suddenly release it.)

HINT: If a malfunction exists, the malfunction indicator lamp will light up when the engine quickly raced.

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





DIAGNOSTIC CHART

HINT:
- If diagnostic trouble code 52 is displayed, check No. 1 knock sensor (for left bank) circuit.
- If diagnostic trouble code 55 is displayed, check No. 2 knock sensor (for right bank) circuit.
- If diagnostic trouble code 53 is displayed, replace engine control module.





WIRING DIAGRAM














INSPECTION PROCEDURE


Reference: INSPECTION USING OSCILLOSCOPE:
- With the engine racing (4,000 rpm) measure waveform between terminals KNK1, KNK2 of engine control module and body ground.





HINT: The correct waveform appears as shown in the image above.





- Spread the time on the horizontal axis, and confirm that period of the wave is 151 micro sec. (Normal mode vibration frequency of knock sensor: 6.6 KHz).

HINT: If normal mode vibration frequency is not 6.6 KHz, the sensor is malfunctioning.