In 2007 Ford introduced a newly redesigned Sport Trac and that started Gen-2 (second Generation) Sport Tracs made prior to the 2007 model year were refered to as Gen-1 (first Generation). You have a 2002 which makes it a Gen-1.
Early Gen-1's are known to have problems with the wiring harness in the steering column with the Tilt Wheel. If the harness does not have enough slack it can pull on the wires when the wheel is tilted up or down. Tilting the wheel can cause wires to break or pull out of an inline, multi-circuit connector. This can cause a lot of strange, erratic behavior in electrical components that have wires in the steering column. That includes the Horn, Turn Signals, Lights, wipers, cruise control, ignition, starter, etc. Oddly enough, the tail lights and brake lights go through the steering column wiring.
Sometimes moving the wheel up or down will restore the connection and things will work fine until the wheel ist tilted to a new position.
The cure is to check out the wiring harness under the steering column and see if there are any broken wires or wires pulled out of the inline connector. If so, they need to be repaired or replaced. Then you need to insure that there is enough slack in the wiring harness to allow the wheel to tilt through the full up and down range without causing any stress on the wiring harness. This is done by pulling up a bit more slack in the wiring harness.
All this assumes that you have check the tail light/brake light bulbs and know that they are good. They are two element bulbs...one element bulbs...one for the tail lights and the other for the brake lights.
Good luck.
...Rich