S60 Anti-Theft Alarm Malfunction

I have an S60, and that sounds vaguely familiar. Is there any chance your alarm system is coded to activate optical locking, meaning the indicators flash instead of the horn sounding? I had some weird electrical gremlins pop up that were triggered by that setting. Any work done on the car recently, especially related to the battery?

Thanks for the swift reply! Optical locking... that's an interesting point. I haven't knowingly changed that, but is there a way to confirm if that's the case without diagnostic tools? And the battery is the original one, though it seems to be performing ok... Could a slightly weaker battery trigger this?

Confirming the optical locking requires diagnostic tools, I'm afraid. The battery could contribute, but I'd lean toward module weirdness if it's starting fine. In my experience, if it's not a simple setting, things escalate rapidly with these systems. Just to be safe I would visit your local Volvo workshop to fix this issue.

All right, thanks for the insight; sounds like a trip to the shop is in order. Workshop confirmed that indeed the alarm system was coded to activate optical locking: repair was 45€. They recoded it properly and everything seems fine now.