tow haul button wont work

I've got a 2003 GMC 2500HD 2WD 6.0L . The tow haul suddenly wont work and the indicator light on the dash board wont work either. Does anyone know if there is possibly a fuse for this because I cant find it in either fuse block. Or tell me where it conects to the tranny and I can check for loose wires. Thanks for the help. I'm hoping this doesnt start a transmission problem