Couple of things. Number one - when you are towing, if you activate the brakes manually do they work. This point is extremely important because you can not feel the trailer brakes working given the controller uses an accelerometer which mimics the stopping of the truck, when using the brake pedal. You simply can not feel the brakes on the trailer working with any of the new controllers either OEM or aftermarket. They really are that good. If they trailer brakes works manually, your controller needs to see a dealer, pure and simple. If manual also does not work, again this is a connection issue.

Number two - "check trailer" normally comes up due to the connection between truck and trailer. It does not mean the trailer brakes are not working. It means the TBC in you truck is looking for a set resistance from the magnets to tell it everything is working as it should and it is not getting the correct resistance. This is almost always a plug issue or a grounding issue between the truck and trailer. The controller is the least likely suspect in this situation.

Steve