So I dealt with my first engine light yesterday in my 09 H3 w/3.7L. I went to a local O'Reilly and got them to read the codes for me:

U1017 - Invalid or missing data (lost connection)
P0014 - Camshaft (B) timing over advance
P0442 - Evaporative emission control system leak detected

I had also been getting TPMS error messages consistently about every other time I cranked the vehicle... I just had new tires put on and TPMS were rebuilt on each tire about 600 miles ago so I was confused as to what the issue was.

Now I'm not sure how many codes it takes to set off the check engine light. I did some relatively simple maintenance, not expecting to change things, but things that needed to be done:

1) Cleaned battery terminals (some corrosion on positive terminal), battery box, reconnected everything and put grease over terminals to prevent future corrosion build up. Also filled battery slots with distilled water to max levels (was a little low in all cells). O'Reilly did check my battery and while it tested good, it said it needed to be charged, and the alternator tested good too... so we suspected a loose connection to the terminals. I also protected some overexposed wiring on the positive terminal cable.

2) Air filter was in upside down... how can you tell? There's a little offset tab on the box towards the front of the vehicle. If you put it in upside down, it's very hard to re-seal the box (but apparently possible). I'm pretty sure that air was entering/escaping behind the air filter. Maybe this was responsible for the last code, maybe not. Air filter is brand new-ish, very little dirt and grime. I've only had this vehicle for about 2000 miles.

3) I re-protected some wiring to sensors that branch off the wiring bundle running to the spark plugs on the passenger side of the engine up front. The plastic wiring protection was dry-rotted and pretty much broke off on a few of the off shooting cables from the bundle, so I disconnected the sensors and put new wiring protection on and reconnected them. I checked all other wiring for dry rotted or old protection as well. This was more preventative maintenance to keep from melting some wires on the engine.

4) I folded in the mirrors and overnight, added a little bit of JB Weld to the mounts to tighten up the plastic-to-metal hold. The driver's side mirror was wobbling BAD in the wind and it doesn't move at all now. The passenger's side mirror was a little loose before and now it's very solid.

So I've been in and out of the vehicle three times now and no more check engine light and no more TPMS messages. I'm confused as to a few simple things that I was going to do anyway cleaned up the mess. Maybe if was the battery connection? No clue.

 

The OEM battery cable ends are CRAP and are the main cause of many electrical gremlins in our H3's.
Many codes will show up just because of the poor connection to the battery. The BCM that controls most of the vehicle functions is very sensitive to voltage fluctuations and loose connections are a bad thing.
Many of us have replaced the battery cable ends with new quality connectors like the ones from Tsunami or Stinger.