Outline Of Diagnosis
WARNING: This page is about a different car, the 2006 Subaru Outback. 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 main CPU normal RAM, or the sub CPU normal RAM, judge as NG. Judge as OK when both are operating properly.
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.