I got one of these for my Subaru. Only used a trailer a few times. After 3 years the unit failed and when a trailer was connected all it would do is turn on one tail light at all times, even with the car off. Brakes and blinkers did nothing.  I needed to go on a 60 mile trip and couldn't find one of these local, plus I wasn't very happy with it only lasting a few years. So instead I went ahead and made my own adapter using two automotive relays. Luckily I had the relays available as I had trouble finding them near by. Could only find ONE for $20 at a car parts store and that price is ridiculous. You can get them on eBay or Amazon for less than $3. 

So if anyone wants to make their own DO AT YOUR OWN RISK! but here is what I did

Brown wire connects straight through

White wire (ground) also connects straight through but you need to tap into it for the ground connection on the two relays.

Brake connects to the switch side of both relays that is connected when the relays are not powered on. 

Left turn is connected to the Left relay coil. Right turn is connected to the Right relay coil.

When the brake lights come on, power will be sent to both trailer lights.

When the left relay is powered by the left signal (blinker), the left trailer light comes on. Same for the right.