I recently picked up a hitch receiver for cheap off craigslist for my 940 with the intention of using it for a bike rack. However I figured I might as well wire up a trailer lighting connector in case I wanted to rent a uhaul. Buying the common 4-pin connector is cheap and hooking it up is pretty simple, except I needed to convert from 5 wire (ground, taillights, brake lights, left turn and right turn) to 4 wire (ground, taillights, combined left turn and brake, combined right turn and brake). European cars usually have separate turn and brake lights, which needs to be adapted to the combined turn and brake lights used on trailers. You can buy adapters that do this but they're kinda expensive ($20+) and draw their current from your car's taillight wiring, which can overload them if your trailer doesn't have led lights. You can add isolation relay to draw power from a separate 12v source but that adds more cost onto the lighting adapter itself.