There are 2 wires for the O/D Cancel button and they make a right turn as they come out of the hollow shift shaft to go down the top of the column. Sometimes these wires chafe through the insulation and short intermittently to the shifter when it is moved or when the truck hits a bump. Pull off the upper column trim to inspect them
having trouble with removing the upper column trim rmoved 4 screws but the cant get the trimoff the column

 

my old truck did the same thing, move the shifter around until you have enough space to pull the trim off, also if you have a tilt column you can move that around. if all else fails pull the radio bezel kick panel and then the dash bezel and then it will come out super easy.

 

thanks