Outline Of Diagnosis
WARNING: This page is about a different car, the 2013 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.
Detect the malfunction of microcomputer (RAM).
When there is a problem in the CPU normal RAM, judge as NG.
If it is possible to write data to the whole area of RAM in the initial routine, and is possible to read the same data, it is judged as OK, and if not, NG.