96 dodge ram transmission

I have a 96 ram 1500 4 wheel drive, it was working fine and the next time I got into the truck to go somewhere I could not get the truck to get out of 1st gear on the automatic trans. I did not know if this was a trans problem or a computor problem so i shut off the truck and turns the ignition key 3 times and got a default code of 1-2-5-5 .I don't know what is happening ,can anyone help me on this.