You know, there is more to a to a tow hitch on a Mercedes than connecting to a trailer. It uses the light system to tell the computers that there is a trailer attached. That modifies the braking system and much more.

I've never been completely satisfied with the factory tow hitch/lighting on my 2014 ML350. As you say, it interacts with the lighting and braking, but at least in my case in strange ways:
- I regularly get 'check trailer left/right rear light/brake light' warnings, and dutifully check them only to find they're OK
- more seriously, something odd happens with braking on steep downhill gradients causing the vehicle/trailer combination to feel quite unstable. It feels like the ABS is being activated on one side. Time to visit the dealer.

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