Hi,
This post has been around for a while but we experienced the identical problem over the weekend (August 5, 2018). In June of 2018 we purchased a 2012 Legacy Premium with 113,200 miles. A one-owner that looked like it just came from the Showroom. I had the Timing Belt job done (complete) by an Indy shop in West Allis, WI (Midcoast Auto; http://www.midcoastauto.com) that focuses on Subarus; Timing Belt Job, Head Gaskets, Heads, and Short Blocks.
My research on the above referenced multiple warning light surprise lead to another Subaru blog that identified it as a Subaru electrical mystery that to date there is no factory diagnosis or fix for. The interim fix is to simply clear all of the codes and unless any of them reappears, just keep driving. That simple. No cost and nothing to worry about at this point. If you don't have a CODE reader get yourself an Actron CP9129 from Amazon or similar for ~$40 and you are set for life.
Hope this helps.
Arturo,
Chicago suburbs
For what it's worth, we have a 2012 Legacy that we bought about 15 months ago with ~113,000 miles at the time. We had all of these check engine lights that would not stay off. I did the Gas Cap and even changed the Throttle Body. It was not fixed until I replaced both of the Oxygen Sensors that it all went away. It is actually an easy job once you have the right tool. Both parts and the tool from http://www.rockauto.com were less than $200. No more "Check Engine" lights and we're approaching now 124,000 miles. There a couple of how-to videos for this job on youtube. Hope this helps. Arturo 10/15/19