Is the dealer the only one who can reflash the TCM? I want to do a o/d lockout switch, truck was built in 11/01.

Is there any way to tell if it was updated? The tranny was last worked on in 2/03 by dealer.

To my understanding, the tcm will need to be reflashed after the lockout switch is installed to make the needed changes in programing. I installed one in a customers veh about 1 year ago, and if I recall, the reflash was part of the operation after parts installed.

On build dates after approximately March, 2002 the necessary software to accomodate the OD Lockout was installed from the factory. Your situation is like mine, your truck was built in 11/01 and therefore the software has to be updated. Unless you have complained about an issue related to the transmission, it is unlikely that they just updated the software. The dealer should be able to determine what software version is currently installed in the TCM

When they updated the TCM software for me, they noted a 1/2 hour labor charge for TCM update and fast learn procedure. So figure worst case a 1 hour labor charge (maybe $80-$100, depending on the labor rate).