A few days ago I noticed that the horn had stopped working. The fuse is fine and the sound is there (the car honks during the lock-up as usual), so I'm thinking about checking the horn relay before submitting the car to the dealership. I guess it should be somewhere in the fuse box, but I've never dealt with relays before and the manual doesn't have any info on this, so I would appreciate a nudge in the right direction greatly.

Found it! In case anyone else is interested, it's T03. See the attached diagram for convenience.