The Mercedes Benz ML320 is a practical, luxurious and high quality SUV that represents a German approach to truck making. Many owners choose to install a trailer hitch, which makes the ML even more practical by making it possible to tow a trailer. The fact that Mercedes predrills the ML’s metal bumper at the factory to be able to take a trailer hitch makes this a relatively straightforward conversion.
Pry open the three plugs in the bumper cover that conceal the screws that hold the bumper cover on. Use a screwdriver to remove the screws.
Remove the safety cable for the rear mud flaps if your ML has mud flaps. Pull the bumper cover off by carefully sliding it straight back and set it somewhere where it won’t get scratched or damaged.
Install the guide bushings that came with the bumper hitch into the guide holes in the ML’s frame. The frame already has holes for the bushings. Install the trailer hitch braces by inserting the supplied bolts through the brace and the guide bushings. Tighten the nut onto the bolt with a ratchet.
Bolt the supplied spacers to the bumper. There is one spacer for each side of the trailer hitch and the holes are predrilled from the factory.
Pry open the plastic cover on the driver’s side of the ML located at the inside rear of the car to access the wiring harnesses for the rear end. The wiring harness plug should be visible once the cover is removed.
Locate and remove the rubber plug on the inside of the bodywork that covers the hole for the trailer hitch wiring harness. Guide the supplied wiring harness through the hole. Install the supplied rubber plug in the hole along with the wiring harness.
Disconnect the ML’s main wiring harness, turn signal indicator and brake module and plug them into the plugs that are on the new wiring harness. Replace the plastic cover that conceals the wiring.
Install the trailer hitch onto the bumper, using the predrilled holes in the bumper and the supplied hardware that comes with the hitch. Use a torque wrench to tighten the trailer hitch bolts to 118ft. lbs.
Install the wiring harness bracket onto the predrilled holes in the bumper. These are small and may appear to be covered in paint but are there. Install the wiring harness onto the bracket. Install a 25-amp fuse into the slot numbered “F18” on your fuse box.
Use an X-acto knife to cut a hole for the trailer hitch in the plastic bumper cover. The hitch will come with dimensions and directions for the proper hole size. Reattach bumper cover by sliding it over the guides and then installing the screws that hold it on. Reinstall the rubber caps that conceal the screws.