Subaru BRZ 2017 Owner's Manual page 479

Vehicles with a manual transmission
Set the parking brake.
STEP 1
Put the shift lever in neutral.
STEP 2
Turn the push-button ignition switch to "ACC" mode.
STEP 3
Push and hold the push-button ignition switch for about 15
STEP 4
seconds while depressing the brake pedal and clutch pedal
firmly.
Even if the engine can be started using the above steps, the system
may be malfunctioning. We recommend that you have your vehicle
checked by any authorized SUBARU dealer or repairer, or another
duly qualified and equipped professional.
5-2. Steps to take in an emergency
5
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