2004 6.0 auto tranny not downshifting.

[crrider08]

I am on vacation right now and on the way here my truck would not downshift coming up hills with abput 12k in the fifth wheel. It has stock gearing and 315's on it but has pulled flawlessly many times before with the same setup. It throws no codes nor does the tow haul light flash. It drives perfectly fine without the trailer and once i make it over a hill it still will not downshift until i pull over and shut the truck off and restart it. Any help would be greatly appteciated because 5mph on the shoulder sucks!

Sorry for the typos im on my cell phone lol

[BigFuel]

Manually shift till you get home. Use the PRiNDL and tow button to move up and down the shifting range. It ONLY does this with the trailer attached??? I'm thinking pigtail wiring (doesn't know it has a trailer hooked up), bad MAP sensor (doesn't realize the load on the engine), or tow fuse. Do you have a "newer then the last time you towed" chip or tuning??? Remove the chip and drive on.

Where are you?

[crrider08]

The truck is bone stock except for the 315's and leveling kit. Motor is stock. It only has 80k on it. It only does it with the trailer hooked up. Ill check the wiring for any shorts or loose connections before i leave in the morning. Im in pismo beach and im traveling back to sacramento, so there arent many hills to get over but theres 2 or 3 good pulls where the truck gets down to 20-25 mph.

[BigFuel]

Cool. Have a safe trip home. I'm still thinking pigtail and that for some reason the truck doesn't know it's towing a trailer. ...might...still be the MAP sensor not seeing proper boost levels (dried cracking hose, or it came undone) so it doesnt realize the motor is loading up with the trailer.