I have never heard of the "Check Engine" light coming on for service. The only reason my light will come on on my 99 ML 430 is if there is a problem with trouble codes. Any OBD II can read these codes for you or you can get them done for free at any Advance Auto or Auto Zone.
You can try cleaning your mass air flow sensor with a non-corrosive fuel injector throttle body cleaner like I did. It is only a temporary fix if that is the problem ( make sure it is before you clean it! PO170 and PO173 were my codes). I bought myself about 1000 miles every time I cleaned it but I finally replaced it. These things are FLAKY!
Whoever reads your codes should be able to tell you what they mean.
As for service lights, a little wrench usually shows itself every time you start your vehicle. You can reset it per instructions in your owner's manual. GOOD LUCK!
The following instructions need to be followed very carefully. It took me two tries the last time to reset it!
1.Turn key in steering lock to position 2.
2. Immediately press the button to the left of your odometer (referred to as button 1) twice within 1 second.
3.The present status for days or distance is displayed. Within 10 seconds turn key in steering lock to position 0.
4. Press and hold button (1) while turning key in steering lock to position 2 again. The present status for days or distance is displayed once more. Continue to hold button (1).
After approx. 10 seconds a signal sounds and the display shows 10,000 miles (Canada: 15,000 km) for approx. 10 seconds.
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