Procedure To Switch To Service Diagnostics Mode

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: Locating Buttons For Switching Service Diagnostics Mode
Courtesy of SUBARU OF AMERICA, INC.

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