Mercedes-Benz GL-Class: Coupling up a trailer - Trailer towing - Driving and parking - Mercedes-Benz GL-Class Owner's ManualMercedes-Benz GL-Class: Coupling up a trailer

WARNING While you are coupling or decoupling a trailer, 
While you are coupling or decoupling a trailer, make sure nobody locks or unlocks the vehicle and/or opens or closes doors or the tailgate.
The vehicle's level could change and you could endanger yourself and/or others as a result.
Make sure that you do not operate the ADS button or the vehicle level control system when coupling/decoupling the trailer.

Observe the maximum permissible trailer dimensions (width and length).

Most federal states and all Canadian provinces require by law:

safety chains between the towing vehicle and the trailer. The chains should be crosswound under the trailer drawbar. They must be fastened to the vehicle's trailer coupling, not to the bumper or the axle.

Allow for enough play in the chains to facilitate turning tight corners.

a separate brake system for certain types of trailer.
a safety switch for braked trailers. Check the specific legal requirements applicable to your federal state.

If the trailer detaches from the towing vehicle, the safety switch applies the trailer's brakes.

(if featured) to the hydraulic brake system Do not connect the trailer's brake system (if featured) to the hydraulic brake system of the towing vehicle, as the latter is equipped with an anti-lock brake system.

Doing so will result in a loss of function of the brake systems of both the vehicle and the trailer.

line to the brake indicator lamp. The vehicle's wiring harness features a line to the brake indicator lamp.

Make sure that the automatic transmission is set to position P.
Apply the vehicle's parking brake.
Start the engine.
Select highway level.
Vehicles with the adaptive damping system: set ADS to AUTO or COMF.
Switch off the engine.
Close all doors and the tailgate.
Couple up the trailer.
Establish all electrical connections.

Vehicles with the AIRMATIC package:

with a trailer attached, the vehicle will always remain at highway level. When coupling up a trailer, please observe the following:

if highway level has not been set manually, the vehicle will automatically sink to highway level as soon as it reaches a speed of 5 mph (8 km/h).
high-speed level is not available.

These restrictions apply to all accessories powered through a connection to the trailer power socket of your vehicle, e.g. a bicycle carrier.

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