I just want to mention concerning the OPDA that there is a link in this string which says the 8th alpha-numeric position of the VIN number, if it is an "S" indicates a potentially faulty OPDA. This is incorrect according to the Jeep/Chrysler Service Shop Manual for the 2006 model year.
According to the manual it states that an "S" in the 8th position merely indicates that the jeep came from the factory, with a 4.0 I6 engine. The only other number/letter possibility for the 8th position in the VIN is a "B" which designates a 2.4 I4 engine. Only an S and a B were used in the 8th position.
In all probability, something this simple would likely translate to all of the TJ years.
I am not trying to minimize the OPDA problem, but merely trying to clarify what I read in the manual.