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Discussion Starter #1
My 1999 E320 has 114K (kilometers) or about 70K miles.

I've had it for about 6 months and it drives really well.

Last night I filled it with gas and today I noticed that the "check engine" light came on. I took off the gas cap and re-tighted it as someone suggested to do. It may not have been completely tightened but I'm not sure. The car seems to be running 100% but the light is still on. Someone told me that you may have to drive it for a few days for the light to go off.

Is that right and how may days should it take for the light to go off (maximum) if it was only a loose gas cap?

Any other suggestions are welcome.

thanks
 

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It was fun while it lasted
2002 ML320, 2005 S430 4MATIC RIP, 2010 F150 Crew Cab
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11,143 Posts
I understand that it takes three on-off positions to clear the check engine light after the problem has been corrected. An on-off position is classified as a start and drive for 5 to 10 minutes for the computer to run it's internal diagnostic to make sure the problem has been corrected. If your light is still on after 3 or 4 days of driving, then you have another problem.

You can take your car to Advance Auto or Auto Zone and have an OBD II diagnostic run free of charge (dealer charges 70 to 100 bucks). They can tell you the codes and what they mean. Oxygen sensors and Mass air flow sensors are notorious to fail in Mercedes and one of these is most likely the problem.
 

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Discussion Starter #3
Thanks for the info and advice. I was starting to freak out when I saw the check engine light on but it does not sound serious especially when it semms to be running 100%.

I may have slightly overfilled it on gas last night too and wonder if that may be the issue? When I removed the gas cap to tighten it, it was a bit wet with gas.
 

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2004 Lexus LS 430 Modern Luxury. 2012 Acura TSX (fun fun) Maybe MB again one day...
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Have the codes pulled.

I bought a pocket scanner for 80 bucks or so.
 
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