Most cars, excepting some made in North America exclusively for the dumbed

down North American market, have separate wiring for amber turn and red
brake lights.

The adapter box on the trailer harness for my Subaru combined the brake and

turn wires into a single wire for each side (3 into 2). It got
unceremoniously
chopped off after it gave up the ghost.

Hint: Unplug the harness before cutting to save on fuses.

Newer Cobra trailers have a terminal strip at the back where North
Americans
have an unfortunate habit of mucking things up.

So yes, make up an adapter between the plugs.

Some day I will add diodes to mine.