Tractor Truck

I have an 02 4WD auto. I have had the P1693,P0500,and P0216 codes for over a year now. I usually get the dead pedal for about a mile in the mornings and in the evening leaving work. Occasionally the pedal will drop out and I just release it for a few seconds and then most of the time it will pick back up. Well today I went to the store during the middle of the day and the truck would not shift out of first gear. RPMs would go up to 3K if I tried but the speed would slowly go up. I have 4.10 gears so first gear does not get me anywhere fast. I tried to shift it manually but it made no difference. I release the throttle and pressed it again several times but no luck. I did get it to shift one time by cycling the throttle and it went to third but as soon as I stopped at a stop light, it went back to first and stayed there. Where do I start to figure this out and correct the problem?
Thanks in advance
Ray

annabelle

Replace the gov. pressure solenoid and sensor. Might well change the tranny filter while you are at it. You will need to drop the pan.....easy job though......I've replaced mine twice.