48RE will not shift into high or OD

Just returned from a 4500 mile RV outing with new 2003 HO 3500. The truck has 9000 miles on it now. On the way, to work last Monday it failed to shift into the high gear then failed to go into OD.Local Dodge dealer has had it for 3 days and still could not find the problem. This is pretty upsetting to me seeing I have only had the truck for 5 months and only has 9000k miles on it. Has anyone else has experienced this problem and if so can you tell me what the problem was? I have about given up on my Local Dodge dealer to figure it out.
P.S = Pulled a 25 ft 7000lb 5th wheel on the 4500 mile RV out just before this problem started.

 

Search the 3rd gen area for posts on this subject. From what I remember there is a problem with the plug on the JTEG that controls the tranny from the PCM.. I remember reading that just cleaning the plug or re-plugging it seemed to fix some related problems.

Give it a go if you don't get a quick response.

J-eh