ETC control unit, location - GF27.19-P-4012-01GG
WARNING: This page is about a different car, the 2009 Mercedes-Benz E550 and 2008 Mercedes-Benz E550. However, it is still accessible from the selected car via links, so may be relevant.
Transmission 722.6 in models 129, 170, 202, 203, 208, 209, 211, 219, 240
Shown on model 170
Location
The ETC control unit (N15/3) is installed under the tread plate in the front passenger footwell.
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.