If it is the same as mine (1991 190E 2.6) it is in the trunk (passenger side) between the trunk hinge and the fender well.
1994 C280, dark green metallic
1991 190E 2.6, Black
(sold to another forum member)
2003 Chevy Tahoe LT, Redfire Metallic
1989 Mustang GT Cobra Convertible