I am not sure if your truck has the same plug as what is listed in my service manuals, but see if there is a 6 wire plug going to the brake light switch. If so, there should be power at terminal #1 which should be a pink with dark blue striped wire, and when the brake pedal is depressed there should be power at terminal #2 next to it. There should also be continuity between terminals #1 and #2 when the pedal is depressed. The manual doesn't say what color that wire is. If no power is at terminal #2 when you push the brake pedal down, the switch is bad. There should also be contunuity between terminals 3 and 4 when the pedal is depressed. The wire terminals are numbered from 1 to 6 reading left to right as you look at the plug on the switch with the locking tab facing up. It should not be too hard to replace and I would guess is not a very expensive part.