Scotty, 2008 Grand Cherokee Overland w/5.7 HEMI. 219,000 miles. I have an excellent mechanic who trouble shooted everything possible regarding persistent cat codes, P0031, P0133, P2096. Replaced O2 sensors, cat was replaced at 185,000. Has tested all wiring to confirm connectivity. Could not get the car to get through drive cycle so... Here in Massachusetts I could not pass emissions test. Bit the bullet and ordered a preprogrammed replacement PCM, $249... Ouch. Still occasionally trips P0031 but will go through drive cycle for a few days before engine code hits.  Passed inspection!  Any ideas? Love the Jeep... I know you don't... But my Overland was bought 5 years ago with 165K for $5,000 so I've done OK so far.