This from a Subaru master tech:
Subject: Subaru Service Program WQC-39: ECM Reprogramming
2011-2012MY All Models & 2013 BRZ; Only Vehicles Registered in California Emission States: CA, CT, MA, MD, ME, NJ, NY, OR, PA, RI, VT, and WA.
Subaru of America, Inc. has initiated a Service Program to reprogram the Engine Control Module on all 2011 and 2012 models within specific VIN ranges and certain 2013 BRZ models. This program only involves vehicles that are registered in the California emission states (CA, CT, MA, MD, ME, NJ, NY, OR, PA, RI, VT, and WA).
A modification to the ECM software logic has been developed to improve the monitoring parameters within the On-Board Diagnostic (OBDll) system for the engine coolant thermostat. This correction ensures that should there be an abnormal condition (i.e., the engine coolant does not reach or maintain the proper operating temperature), the “check engine light” will illuminate. The proper illumination of the “check engine light” is needed to alert the driver that corrective action may be required.
ECM reprogramming PAK files will not be available for all models at the time this Service Program is initially released. PAK files will be available in accordance with the schedule found on page 4 of the WQC-39 bulletin. Additionally, because this program affects a high volume of vehicles within the affected states, mailing of owner notification letters will be phased according to the following schedule. This schedule coincides with PAK file availability.
Ok, thats the official stuff here is the lowdown. So far we have seen one new car with a cel with a code for the coolant tempature/thermostat.
We do not have the updates for all the cars yet and they will be released in a schedule along with the letters to the owners. Unless you get the cel on, I wouldent make a special trip to the dealer for the reflash; get it when convenient for you.