thanks for the tips and sorry its a 1988 E300 and to answer with the car locked and key in pocket the check engine light glows but only when its real cold and left out side over night - when you turn the key to start is comes on bright but as the car warms up 5 / 6 min it goes out and stays out, than sometime during the time you leave it parked again and come back if it has gone below 35 it starts to glow again ???? BUT if its in a parking garage and it is not in the real cold it does not come on -- only at start up than goes right off as it should --

i will go and check for the alarm under rug and see if its that ( disconect it )

but it has no affect on the car other than being on when you get in the car, in the very cold day or night -- jz