Ahh a 2012. Big differences pre and post-2007. My buddy
@Czechsix had a 2012 and bought all the fancy dialogistic equipment. Pretty pricy if I recall but it helped a lot with all of the issues he had, I tagged him in this post so he should chime in hopefully
(if he is not out hiding on some ridge). He is a smart guy so his advice
will should be invaluable. I can't speak to a 2012, but I went through a lot of fan belts on my 2002, so I'd add both fan and AC belts. Spare lugnuts (LH.RH) if super singles and spare lug studs (LH.RH) if running duels. A set-up to break the lug nuts, either a multiplier or a support set-up (see below). A large torque wrench so the lugnut can be properly torqued, especially after a tire shop has worked on it. You probably already have it in your kit, but a good multimeter and tools/brushes to clean electrical connections and dielectric grease. Grounds (at least on older models) can be a problem.
Takes a while to go up and down the ridge, right
@mog?
So I carried the full manual set, belts, hoses, assortment of fasteners, a Deutsch connector repair kit, a good multimeter (I used the Fluke 88V), the usual baling wire/duct tape/gorilla tape/JB Weld/epoxy/various RTV sealants/hose clamps/zip ties/etc, a complete Star/Xentry diagnostic system (Toughbook/harness/connectors/software), torque multiplier for the lug nuts, a decent torque wrench, spare lugnuts, lots of tire fixit supplies (reamers, plugs, tire boots, sealant). Three hydraulic jacks, an offroad specific jack stand system. HiLift jack. Sand ladders.
Spare parts I carried were two complete sets of filters, two complete changes of fluids, two PCV replacements (big problem on the 2012 and others, it's a dumb overly complex system), DEF system parts (another PITA system).
Add in a good air compressor (I carried...you can probably guess....two), a few good tire gauges, a good tire monitoring system. Past that, various tools. The usual mechanics set, plus specific tools to work on medium duty trucks. Prybars, large torque wrenches, large wrenches, portable MIG welder, small generator, various battery powered hand tools like drills, impact drivers.
Oh, and satcom when you have to call the regional FUSO rep to figure out what that damned code means. The one that's not in the manual. It's documented in the new update that's not available yet. Local mechanics have no idea what it is, but they'll call back east to find out.
Anyway, it sounds like a lot, but it's not. I know mog carries a full Bridgeport mill and a 10x36 lathe when he goes offroad, so I use that as my standard for comparison. I go lightweight, relatively speaking.