HELP! MAF replaced, but Check Engine Light still ON!

[you89]

Hello, I have 2002 S500.

I replaced the MAF.. and recovered a lot of power. I could not believe how much torque I got by replacing this sensor.

anyways, about 3 days later.........
Check Engine Light came on.

I do not have a code scanner. I might buy one for myself.

I don't think it is the gas- I checked the gas cap, but it was already tight. I did the gas cap again, but no luck even after 5 ignitions over 2 days.

Now, I am guessing if this could be related to O2 sensors. Any suggestions?

one more thing, when you remove the MAF sensor assembly, there is rubber notches on the rubber o-ring for sealing between 90 degree bent tube. This rubber is old, so it is pretty hard- I was not able to put the notches into the notch sockets on the 90 degree bent tube. could this let some unfiltered air to flow into the intake and trigger the engine check light?..