I hadn't drove my 2008 dodge ram 1500 sxt truck for 2 weeks. then driving it down the interstate all of a sudden the RPM's raise high and it drops in speed, i got it back home and tried to drive it again, now it wont shift into 3rd gear. i bought the truck in 2010 but my warrenty ran out in november from what they say. A mechanic informed me it was the TPS? where is that and can i fix it myself, or can i reset it somehow?