Mercedes-Benz GL-Class 2013 Owners Manual - Manual (Page 222)

i PARKTRONIC is automatically activated
when you turn the SmartKey to position 2
in the ignition lock.
Towing a trailer
!
Fold in the ball coupling if the trailer tow
hitch is not required. PARKTRONIC
measures the minimum detection range to
an obstacle from the bumper, not the ball
coupling.
PARKTRONIC is deactivated for the rear area
when you establish an electrical connection
between your vehicle and a trailer.
220
Driving systems
Driving
and
parking