Intermittent Tow Haul

I got a 2008 GMC Sierra Denali 1500 with the 6.2 6L80 transmission. My issue is I was just on a 1000 mile trip to pick up a boat and on my way out my tow haul worked great because I was using it on the long rolling hills. On my way back while pulling the boat my tow/haul would not engage while In drive but if I put the truck in manual mode it would engage. I could shift the truck back in drive and the tow haul light would stay on and it seemed to work. I was unable to turn off tow/haul with the button. I had to shut off the vehicle and restart it then it would turn off. Anyone have any ideas?

Fixed it, pulled apart the steering column and found one of the white wires were broke and one of the black wires only had a couple strans of wire left so I spliced in a couple of wires and now it turns on and off.

Sometimes it's the simple things, even if it's not easy to access those things to do "simple" repairs. Hopefully you did something to protect the wiring better so it doesn't recur sometime in the future.