Seat Tarraco siren communication fault

Siren communication fault on a Tarraco, eh? I've seen similar on other VAG vehicles. First, double-check the basics: is the car battery in good condition? A low battery can cause all sorts of weird errors. Also, have you had any recent work done on the car, particularly anything involving the wiring? Sometimes a carelessly routed cable can cause interference. If the error is persistent, and the alarm system is genuinely non-functional (test it!), then yes, a defective cable or plug connection is the most likely culprit. Intermittent faults can also happen due to corrosion. Has the vehicle been exposed to a lot of moisture?

Battery seems fine, no recent work done either. How easy is it to check the cable/plug myself? Don't want to mess anything up more than it already is.

Given it's a safety-critical system (vehicle security), and you're not super familiar with automotive electrics, I'd definitely recommend you take it to a workshop. Modern car wiring can be quite complex, and you could easily cause further damage or trigger the airbag system if you're not careful. The 95€ quote sounds reasonable for diagnosing and repairing a wiring issue related to the siren. I doubt an alarm reset will be necessary after the wiring issue is resolved, but the technician will be able to confirm. It is better to be safe than sorry.

Thanks for the info, I'll get it booked in. 95€ seems reasonable enough to sort out a potential vehicle security breach. Cheers!