Mercedes-Benz M-Class Owner's Manual page 196

If indicator lamp : lights up, PARKTRONIC is
deactivated. Active Park Assist is then also
deactivated.
i
PARKTRONIC is automatically activated
when you turn the key to position 2 in the
ignition lock.
Towing a trailer
PARKTRONIC is deactivated for the rear area
when you establish an electrical connection
between your vehicle and a trailer.
! Fold in the ball coupling if the trailer tow
hitch is not required. PARKTRONIC meas-
ures the minimum detection range to an
obstacle from the bumper, not the ball cou-
pling.
Driving systems
193
Z