Two issues:
1. Ever since I have owned this truck the OD-off button has not worked. I can press and hold it for it to light up. let it go it goes out. Either way it does nothing- no effect on trans operation.

2. No shifting into over drive, at random, after start up.
Some days it works as it should. Other days, it makes me pull over, shut down the truck, and start over to get the shift. This can take 2 or 3 cycles of I/O to get it to work. If it does make the shift it's fine till the next time it acts up - after a start up.

Ideas ? Are they the same issue and connected? I have learned never to assume even being the same system ...

 

Check the wires where they enter the column from the shifter. Known to get broken/damaged.

 

I agree with Lazy, follow wires and look for any kinks, splice, or disconnects, before you do follow the wires though check voltage readings and see if the voltage is correct going to the tranny.