So we brought home our new '17 Legacy 10 days ago. I put a new winter set of wheels and studded tires on, with TPMS sensors. Subaru is the first brand car I've ever owned that needs special tools to make the car communicate with the TPMS sensors. ATEQ has a new tool, the VT-36 that states it programs the sensors and works with Subaru vehicles, but it does not. It only reads them. You also need the ATEQ Quickset. Together you can read the new sensors, and then program them into the Quickset and plug into the OBDII plug. Directions aren't perfect, but the system works. After uploading the new sensor numbers into the ECU, and driving the vehicle over 25mph for a couple miles, the TPMS warning light and message goes away.
On various sites, there are all sorts of work-arounds to disable the light, cover it up etc. I believe tire pressure is extremely important, and having a system to continuously monitor it is a huge safety bonus. To disable that would be a kin to disabling air bags. Sure, I could have gone to the dealer, and for between $50/$100 per season, had them program it - but that doesn't account for my time and aggravation. So for a couple hundred bucks, I can change my sets of wheels/tires as often as I wish.
If anyone needs assistance with the process, pm or email me. Thus far we love the car, still getting use to it.