I have a 2011 outback, which just started with a clicking sound, regularly and every few seconds, underneath the passengers seat, even with the key off. It drains the battery. It sounds like a relay clicking. Is there a relay under there? What else could be causing it? Thanks in advance.

Have you tried pulling fuses to see what circuit has gone gerfarkt?

Can you see any relays beneath the seat?
Have you recently installed any aftermarket equipment? radio, lights etc?

Make sure nothing has been jammed beneath the seat. water bottle, kid's feet that could have disengaged a connector.

front or rear pass seat? Some newer models regularly do an evap pressure test. If it is clicking more than 3-4 times a day however, could be a failure of some sort.

is the CEL on? maybe scan for codes.

Did you ever figure out this issue?

Experiencing the same issue with my Outback