Transient cross firing!

Started with 7/8 tank of gas.  Last Thursday we drove ~42 miles to the Tunbridge Worlds Fair.  Parked for 3 or 4 hours.  Started for home and stopped at a bicycle shop in Rochester VT.  This was just after a long decent over the Bethel Gap.  Stayed ~45 minutes. Got back in the truck and it would barely run!  Running at idle very rough ~600 rpm, engine wouldn't accelerate even in Park.  Popping and banging, backfiring through the throttle body.  2 restarts showed no improvement.  Got engine up to ~3000 rpm in Park and tried to drive north on VT100.  Got ~100 ft, popping and banging, backfiring.  Not going to make it ~20 miles to home.  Returned 100 ft and parked, rather than breaking totally down in the hilly Granville Gulf where there is no cell phone service. 

Called AAA and had the Avalanche towed to a dealership.  Got a ride home.  Dealer looked at it on Friday, and it was fine...  Started right up and idled normally.  Drove normally.  No codes.  Whassup with that?  No repeat of failure.

Misfire / cross fire should have thrown a code - but didn?t.  They will warm it up on Monday and see if it repeats.  I don?t care for transient catastrophic failures.  Any suggestions?

Fuel pump going out?

BAd fuse to OBD2 port?

Well, it cured itself.  When it was popping and banging, backfiring thru the throttle body, and barely running, I has it towed to the dealer.  Next morning the tech goes out and it starts right up and runs great...  No codes associated with the engine.  Can?t find anything wrong with it!  Tech suggests that water in the (ethanol) gas may have run to the front of the tank on the long downhill.  When I parked at the bottom of the hill, did not want to restart properly with whatever was in the fuel line.  Sat overnight and was great.  Been running well since.

I?ve been reading up on how ethanol can separate from the rest of the gas if given enough water content.  I'll run a couple of tanks on non-ethanol through the vehicle...