P0325
DTC P0325: Knock Sensor CircuitCAUTION: If DTC P0325 has been set, TCL related DTC U1120 is also set. After P0325 has been diagnosed, don't forget to erase DTC U1120.
Knock Sensor Circuit (Part 1):
Knock Sensor Circuit (Part 2):
CIRCUIT OPERATION
- The knock sensor sends a signal voltage to the ECM [M/T] or the PCM [A/T] (terminal No. 59).
TECHNICAL DESCRIPTION
- The knock sensor converts the vibration of the cylinder block into a voltage and outputs it. If there is a malfunction of the knock sensor, the voltage output will not change.
- The ECM [M/T] or the PCM [A/T] checks whether the voltage output changes.
DESCRIPTIONS OF MONITOR METHODS
- Knock sensor signal does not change.
MONITOR EXECUTION
- Continuous
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
- Not applicable
Sensor (The sensor below is determined to be normal)
- Not applicable
DTC SET CONDITIONS
Logic Flow Chart:
Check Conditions
- 2 seconds or more have passed since the starting sequence was completed.
- Engine speed is higher than 2,500 r/min.
- Volumetric efficiency is 40% or more.
Judgement Criterion
- Knock sensor output voltage (knock sensor peak voltage in each 1/2 turn of the crankshaft) has not changed for 2 seconds.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 7. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Knock sensor failed.
- Open or shorted knock sensor circuit, harness damage or connector damage.
- ECM failed. [M/T]
- PCM failed. [A/T]
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
STEP 1. Check harness connector B-126 at the knock sensor for damage.
Q: Is the harness connector in good condition?
YES : Go to Step 2.
NO : Repair or replace it. Then go to Step 6.
STEP 2. Check the continuity at knock sensor harness side connector B-126.
1. Disconnect the connector B-126 and measure at the harness side.
2. Check for the continuity between terminal No. 2 and ground.
- Continuity (2 ohms or less)
Q: Does continuity exist?
YES : Go to Step 3.
NO : Repair harness wire between knock sensor connector B-126 (terminal No. 2) and ground because of open circuit or harness damage. Then go to Step 6.
STEP 3. Check harness connector B-20 at ECM [M/T] or PCM [A/T] for damage.
Q: Is the harness connector in good condition?
YES : Go to Step 4.
NO : Repair or replace it. Then go to Step 6.
STEP 4. Check for open circuit and short circuit to ground and harness damage between knock sensor connector B-126 (terminal No. 1) and ECM [M/T] or PCM [A/T] connector B-20 (terminal No. 59).
Q: Is the harness wire in good condition?
YES : Go to Step 5.
NO : Repair it. Then go to Step 6.
STEP 5. Check the knock sensor.
1. Disconnect the knock sensor connector B-126.
2. Start the engine and run at idle.
3. Measure the voltage between knock sensor side connector terminal No. 1 (output) and No. 2 (ground).
4. Gradually increase the engine speed.
- The voltage increases with the increase in the engine speed.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES : Replace the ECM or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Then go to Step 6.
NO : Replace the knock sensor. Then go to Step 6.
STEP 6. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 7. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0325 set?
YES : Retry the troubleshooting.
NO : The inspection is complete.