Yaris alarm malfunction

Interesting. I had something similar happen with my Yaris. Was the battery recently disconnected or run completely flat? The car's computer systems are sensitive, and a power failure can sometimes scramble things. It might be worth checking the alarm control module itself, that's the electronic brain of the alarm system. It is usually found behind the glove box. Could be a loose connector or something.

Thanks for the tip! No recent battery issues, but I'll definitely check the alarm control module behind the glove box for loose connections. When you say similar, do you mean the same error stored in memory, and the alarm just plain not working?

Precisely! Same symptoms. Error stored, system non-functional. If checking the module doesn't solve it, I'd recommend having a workshop take a look. They can likely recode or reset the alarm system. The optical locking setting sounds like the most probable cause, but diagnostics with specialized equipment are needed to be sure.

Took your advice and went to a workshop. Turns out the alarm system coding was the issue, specifically related to the optical locking as the scan tool suggested. They recoded it, and everything is working perfectly now. Cost me 45€. Thanks for the help!