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Inspection procedure 3: The malfunction indicator lamp (SERVICE ENGINE SOON or check engine lamp) remains illuminated and never goes out
 
 
 
 
COMMENT
  • In cases such as the above, the cause is probably that the ECM is detecting a problem in a sensor or actuator, or that one of the malfunctions listed below has probably occurred.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this case:)
  • Combination meter failed.

 
 
DIAGNOSIS
Required Special Tool:
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: V.C.I.
    • MB991827: USB Cable
    • MB991910: Main Harness A
STEP 1. Using scan tool MB991958, read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 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.
Is any DTC set?
Refer to, Diagnostic Trouble Code Chart .
Go to Step 2.
 
STEP 2. Check the trouble symptoms.
(1) Turn the ignition switch to the "ON" position.
  • The malfunction indicator lamp (SERVICE ENGINE SOON or Check Engine Lamp) should go out after the engine was started.
(2) Turn the ignition switch to the "LOCK" (OFF) position.
Does the malfunction indicator lamp (SERVICE ENGINE SOON or Check Engine Lamp) go out?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
Check the combination meter system. Refer to GROUP 54A, Combination Meter - Trouble Symptom Chart .