2000 GMC Sierra Trailer Brake Light Problem

I have a 2000 GMC Sierra (2500), I had a brake controller installed right after I bought the p/u. That was about 2 months ago. When I hooked up to the trailer, I didn't have brake lights on the trailer, I have turn signals on the trailer and truck, and have the emergency flasher also on both. I do have brake lights on the truck. I've checked the fuses for the trailer under the hood, and they are good. I've taken a test lamp to the pigtail on the truck and have turn signals and no brake lights. This p/u does have the amber turn signals. I bought this truck used, and the previous owner supposedly pulled a trailer with brakes on it. When I got it, the controller had been removed from the cab. I've also hooked the trailer up to my other p/u and the lights all work fine. I appreciate any help which anyone can give. Thanks

I think with the separate direction lights you need another wire for the brakes to a diode box that you can get at trailer stores and uhaul.
On the older trucks with combined directional lights/stop lights, If the directionals work the stop lights will too