DTC 52
CODE - 52 KNOCK SENSOR CIRCUITCircuit 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.
Detecting Condition
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.
Trouble Code Detection Driving Pattern
Purpose of the driving pattern.
(a) To simulate diagnostic trouble code detecting condition after diagnostic trouble code is recorded.
(b) To check that the malfunction is corrected when the repair is completed confirming that diagnostic trouble code is no longer detected.
(1) Start engine and warm up.
(2) After engine is warmed up, let it idle for 3 mm.
(3) With the A/C ON, perform quick racing (5,000 rpm) three times. (Rapidly depress the accelerator pedal and suddenly release it.)
NOTE: If a malfunction exists, the malfunction indicator lamp will light up when sudden racing is performed.
CAUTION: If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.
Inspection Using An Oscilloscope
- With the engine racing (4,000 rpm) measure between terminal KNK of engine control module and body ground.
NOTE: The correct waveform appears as shown in the illustration.
- Spread the time on the horizontal axis, and confirm that period of the wave is 123 u sec. (Normal mode vibration frequency of knock sensor: 8.1 KHz).
NOTE: If normal mode vibration frequency is not 8.1 KHz, the sensor is malfunctioning.
Diagnostic Chart
Wiring Diagram
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Step 4:
Inspection Procedure