I have a 1500 5.9L magnum off road truck that has healed itself. It has had the P1740 transmission code for a while, even after replaceing the valvebody pressure boost plate. It also had a misfire in the number 4 chamber. I'd given up trying to fix the codes since my truck seemed to run fine and had no big problems. I was even about to change the plenum gasket. Yesterday I checked the codes and there were none. Just P-done. I havn't disconnected the battery or any other electrical work. The only thing I've done in the past month was change the oil, get a new kickdown cable, and wash and wax it. I guess it just needed some TLC.

 

Be weary, mine jumps around like that too. It was running like hell for a little while untill I decided to take it on a road trip. 1200 miles and a weekend later she ran like a champ. Now though, three months later, I've got misfires and codes I cant even find on the internet.

 

maybe it just gave up on you ever fixing it. when you had the misfire code did you notice any decrease mpg.
Also when pcm's start to go bad theyll throw bogus codes.