Bought it roughly a year ago, passed inspection just fine, but it's been peculiar and I'm wondering if it's fine mechanically and just has some weird electrical gremlins, or the whole thing is doomed.

Here's a few things from over the past year:

• Registered P0876, P0430 shortly after buying it, went away and haven't come back.
• P0406 several times the first few months, then went away and hasn't come back.
• U1418 for one day and hasn't come back.
• For one day, and one day only, the gas level meter stopped working.
• Battery completely drained in a few hours despite not leaving any accessories on. Has been fine since.
• Been a few times where, on first start up, the engine would rev and then it would lurch into gear. After that it would drive fine.
• One day where I couldn't get any power to the wheels (and no lurching). It'd crawl forward a little bit, but not enough to get out of the ruts in the driveway — and the same in reverse. After four or five attempts switching between drive and reverse it finally kicked in and has been fine since.
• Now sporadically getting the traction control light, abs light, and messages to service 4WD and elec brake system but driving fine with the exception of once where the traction control light flashed and the Jeep slowed down a lot, before sorting itself out and got power to the wheels again.
• Gas consumption consistently high. Was originally getting 20L/100km (11.7 MPG), but recently changed to 27L/100km (8.7 MPG).

Garage did say, based on the codes, the transmission was on the way out. That was back in December. They didn't have anything to say about the gas consumption and I haven't taken it in about the last round of errors related to the 4WD and brake system. Could that be related to the transmission or a really bad PCM?