Maybe I'm late to the game, but after driving GM vehicles for many years and a few Toyota's...this is something that would have made a big decision in my vehicle purchase. We picked up a lightly used 2014 Highlander XLE AWD last summer and all has been great. I bought this for my wife to haul the kids and have a reasonable level of safety features to aid her in most driving situations. A good part of my decision was that if she was caught in some bad weather....i.e...snow, that with good tires and AWD, her commute would pose less of a risk of being stranded. What really caught my attention to all of this, was if there is...say.....an oxygen sensor issue, or basically an emissions related issue, that the vehicle DISABLES THE AWD SYSTEM! Are you freaking kidding me?! If I'm still able to drive the vehicle, why does the AWD system and stability control need to be disabled? I can understand a transfer case or differential issue, but this is not acceptable. I've been around vehicles a long time, I can see one arguement that the system may not function up to it's full capacity..maybe, but if I can drive it with no other restrictions, why does the AWD and traction control have to be disabled. I'm very seriously re-thinking this purchase and sell the vehicle. I DID NOT buy this to help keep my wife and kids safe, to have this possible situation lurking beneath. Just some info for anyone that may have the same concerns.