Knocking is a phenomenon characterized by undesirable vibration and noise and can cause engine damage. The knock sensor (KS) is attached to the cylinder block and senses engine knocking. A knocking vibration from the cylinder block is applied as pressure to the piezoelectric element. The knock sensor (KS) detects vibration upon increase and decrease in engine RPM and generates a voltage based on this vibration. The ECM controls the ignition timing based on the amplitude and frequency of the knock sensor signal. For example, if engine knocking occurs, the ignition timing is retarded to suppress it. This DTC is set when the frequency goes outside a calibrated level.
The ECM monitors the range of the analog input signal from knock sensor to check sensor failure that is short circuit or open circuit. If the difference between knock signal and noise level is smaller than the threshold during defined time period, the DTC P0325 is set.
Item
Detecting Condition
Possible cause
Case1
Monitoring Strategy
? Signal check
? Short to ground in signal circuit
? Open in signal circuit
? Faulty Knock sensor
? Faulty ECM
Threshold value
? Reference level voltage : < lower limit,f(rpm)
? Reference level voltage : < higher limit,f(rpm)
Enable Conditions
? Engine speed > 2800rpm
? Knock control enabled
? No dynamic knock control
Case2
? Circuit continuity check, pulse test
? Integrator value difference(End value - Startvalue) : <3.7V
Case3
? Circuit continuity check, zero test
? Integrator offset : > 0.234V
? Intergator grasient : > 40 ~ 60V/sec
? Engine speed 1200 ~ 5200rpm
Diagnostic Time
? Continuous
Fail Safe
? The ignition angle correction is determined by function of engine speed, mass air fiow.
Knock Sensor
Normal Parameter (at 20?(68°F))
Resistance
about 5 ?
Ignition timing
Idle
0 ~ 20° BTDC
3000rpm
29 ~ 49° BTDC
This figures show the waveform measured at terminal 1 of knock sensor at idle.
Check if the output voltage of knock sensor at idle is 0.4V
In case the output voltage is over 3.5V
Possible cause : Short in harness check ECM internal problem.