The truck seemed to not be shifting into overdrive

Recently, after driving thru the mountains, I parked for about a day and then started my truck. The MIL came on, and the truck acted like it didn't want to go. I was able to drive home but the light never went out and the truck seemed to not be shifting into overdrive as it usually does on the freeway. I had the codes checked-po700, po731, po876. The dealer could not tell me the problem. Said it could be electrical or transmission failure. I noticed in your forum that a TSB had been issued for what seems like a similar problem. Could this be the same problem, and would the dealer have to replace the parts for me or will I still end up paying for a huge repair bill and how serious is a possible split transmission sump filter. Oh, the MIL light suddenly went off again, but I have noticed that sometimes on startup, it does not illuminate at all like it should.