So the van is new to me. 100K miles on a 4.8L V8. Hooked up my 12' cargo trailer with electric brakes. Pulled fine until I engaged the tow/haul mode. Then it wouldn't shift from 2nd up to any gear. I tried disengaging the tow/haul button, and the light went off on the dash, but still stayed in 2nd. I couldn't shift manually UP. I didn't try going down, as I was on the freeway, and first gear wasn't ideal. I pulled over and unplugged the trailer. Turned off the van and restarted it. It then shifted fine with the tow/haul utton NOT pushed, but the engine light is now on. I initially thought it might be wired wrong with the aftermarket brake controller, but that wouldn't effect the shifting. So my thoughts are in the button. I don't know what the code is yet...but I'm gonna find out. Any ideas?