Mercedes-Benz 2008 M-Class Operator's Manual page 332

!
Do not connect a trailer brake system (if
trailer is so equipped) directly to the vehicle's
hydraulic brake system, as your vehicle is
equipped with antilock brakes. If you do, neither
the vehicle's brakes nor the trailer's brakes will
function properly.
i
The provided vehicle electrical wiring
harness for trailer towing has a brake signal wire
for hook-up to a brake controller.
You should consider using a trailer sway control
system. For further information, contact an
authorized Mercedes-Benz Light Truck Center.
Make sure the automatic transmission
is set to P ( page 185).
Set the parking brake for the vehicle
( page 65).
Start the engine ( page 54).
Vehicles with air suspension program*:
Set the vehicle level to Highway
( page 255).
Vehicles with air suspension program*:
Set the ADS* to AUTO or COMFORT
( page 255).
Turn off the engine ( page 66).
Close all doors and the tailgate.
Attach the trailer.
Plug in all electrical connectors.
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Vehicles with air suspension program*:
When you are towing a trailer, the vehicle level
always remains in the Highway setting.
The following applies additionally when towing a
trailer:
The vehicle is lowered to the highway level
when it reaches a speed of 5 mph (8 km/h)
if not set to highway level.
The high-speed level is not available.
The restrictions that apply to towing also apply
when using accessories that are connected to
the trailer power socket, such as a bicycle rack.
Driving instructions
Towing a trailer
There are many different laws, including
speed limit restrictions, having to do with
trailer towing. Make sure your rig will be le-
gal, not only for where you reside, but also
for where you will be driving. A good
source for this information can be the po-
lice or local authorities.
Note the following points, when driving
with the trailer:
In order to gain skill and an understand-
ing of the vehicle's behavior, you
should practice turning, stopping and
backing up in an area which is free from
traffic.
Before you start driving check the
trailer hitch
break-away switch
safety chains
electrical connections
lighting and tires
Operation
331