Check Back-Up Light Switch (Mt Model)
WARNING: This page is about a different car, the 2017 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.
Refer to "INSPECTION" of the "Switches and Harness" in "MANUAL TRANSMISSION AND DIFFERENTIAL" information. Ref. to MANUAL TRANSMISSION AND DIFFERENTIAL(6MT)>Switches and Harness>INSPECTION>BACK-UP LIGHT SWITCH .