P0325

Knock Sensor Circuit:

CIRCUIT OPERATION
The knock sensor sends a signal voltage to the ECM (terminal 78).

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 checks whether the voltage output changes.

DTC SET CONDITIONS

Check Conditions
- Ignition switch: ON
- 60 seconds or more have passed after the ignition switch was turned on or the starting sequence was completed.
- Engine speed is higher than 2,500 r/min.

Judgment Criteria
- Knock sensor output voltage (knock sensor peak voltage in each 1/3 turn of the crankshaft) has not changed more than 0.06 volt in the last consecutive 200 periods.

TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Knock sensor failed.
- Open or shorted knock sensor circuit, or loose connector.
- ECM failed.

DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)




STEP 1. Check the ground line at the knock sensor connector B-35.
1. Disconnect connector B-35 and measure at the harness side.
2. Check for continuity between terminal 2 and ground.
- Should be less than 2 ohms. If less than 2 ohms, go to Step 2.

If open circuit, repair the wire between the knock sensor connector B-35 and ground. Then go to Step 5.




STEP 2. Check harness connector B-35 at the knock sensor for damage.
If harness connector B-35 is not damaged, go to Step 3.

If harness connector B-35 is damaged, repair or replace it.
Refer to Harness Connector Inspection. Then go to Step 5.




STEP 3. Check harness connector C-60 at the ECM for damage.
If harness connector C-60 is not damaged, go to Step 4.

If harness connector C-60 is damaged, repair or replace it.
Refer to Harness Connector Inspection. Then go to Step 5.










STEP 4. Check harness wire between knock sensor connector B-35 and ECM connector C-60.
If the wire between knock sensor connector B-35 and ECM connector C-6O is not damaged, replace the knock sensor. Then go to Step 5.

If the wire between knock sensor connector B-35 and ECM connector C-60 is damaged, repair it. Then go to Step 5.

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting scan tool MB991502.




STEP 5. Using scan tool MB991502, check data list item 44: Ignition Coils and Ignition Power Transistor
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 44, Ignition Coils and Ignition Power Transistor.
- Ignition timing with the knock sensor connector disconnected should retard more than the ignition timing with the knock sensor connector connected.

If the ignition liming retards, repair is finished.
If the ignition liming does not retard, replace the ECM. Then check that the ignition liming retards.