Inspection Procedure 20

Knocking

COMMENT
- Incase such as the above, the cause is probably that the detonation control is defective or the heat value of the spark plug is inappropriate.

TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Defective knock sensor
- Incorrect heat value of the spark plug.

DIAGNOSIS

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




STEP 1. Using the scan tool MB991502, read the diagnostic trouble code (DTC).

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

1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Read the DTC.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC output?

YES: Refer to, Diagnostic Trouble Code Chart.

NO: Go to Step 2.




STEP 2. Check the ignition timing.
1. The ignition timing should retard more when knock sensor connector B-108 is disconnected than when it is connected.

Q: When the knock sensor connector B-108 was disconnected, was the ignition timing delayed?

YES: Check the following items, and repair or replace the defective items.
a. Check the spark plugs.
b. Fuel quality, octane level.
c. Check if the foreign materials (water kerosene, etc.) got into fuel.

Then confirm that the malfunction symptom is eliminated.

NO: Refer to, DTC P0325 - Knock Sensor Circuit.