2004 e class

check eng ligth comes on,car runs fine,how turn off lite?

Go to the local Auto parts store, they will pull the Diagnostic Trouble Code (DTC) for free.

Example - P0420
Write the codes down, or get a copy.
Respond to your thread , include codes, so we can help.

03 e-class check eng light, a defective secondary air pump,is it hard to replace and where is located? were can it be found besides the car dealer....help please