On the 14-pin connector for the power and illumination connections (and speakers in other Subaru models), pin #6 is +12V Battery/constant-on. The term "Back Up" is meant like memory back up, not reverse gear lights.
Also, in most Subaru models, pin 14 is used to provide +12V power to an antenna booster amplifier. Very few models have a motorized antenna.
Radio reception will be degraded noticeably if the voltage to a Subaru's antenna booster amp falls below 12.0 V.
Head unit pinout abbreviations
|B+||Battery+ (12V direct from Battery).|
|ACC||Ignition powered. +12 V with the ignition key is in the ACC or ON position.|
|ANT+||Power for Electric Antenna. Output +12 V (maximum 150 - 300mA)|
|FR+ or RF+||Front right speaker out|
|FL+ or LF+||Front left speaker out|
|RR+||Rear right speaker out|
|LR+ or RL+||Rear left speaker out|
|FR- or RF-, FL- or LF-, RR-, LR- or RL-, SGND||The corresponding speaker ground|