Procedure To Switch To Service Diagnostics Mode

WARNING: This page is about a different car, the 2016 Subaru Outback and 2016 Subaru Legacy. However, it is still accessible from the selected car via links, so may be relevant.

Turn the ignition switch to ACC.
After turning the ignition switch to ACC and wait for 20 seconds or more, press the button (d) five times with the button (a) pressed.

Fig 1: Identifying Button
Courtesy of SUBARU OF AMERICA, INC.

NOTE: Pressing the button (c) for 3 seconds or more, or turning the ignition switch from the OFF to ACC position can exit the diagnostic mode.