Kuga auxiliary battery alarm issue

Sounds frustrating! That auxiliary battery system can be a real pain. It’s like the car's backup brain, and if that goes, things get weird. When you say 'alarm system without function' do you mean it's completely unresponsive, even with the key fob? Have you tried disconnecting the main battery for a while to see if it resets anything? Also, does the error code give any specifics?

Yeah, it's completely unresponsive. Key fob, door sensors, nothing triggers the alarm. Disconnecting the main battery – I haven't tried that yet, figured it wouldn't affect the aux battery. As for specific codes, just the generic 'Additional battery alarm system defective' message. No sub-codes or anything helpful like that. Is disconnecting the main battery really worth a shot?

Gotcha. The main battery disconnect is a long shot, but sometimes it can clear out gremlins in the system. However, based on those symptoms and the error message, it really does point to that auxiliary battery being toast, especially with that mileage. They tend to degrade over time, like a phone battery that doesn't hold a charge anymore. Sadly, I think a trip to a workshop is unavoidable to get it properly diagnosed and replaced. I’m afraid I agree with the potential cause: ageing battery.

Yeah, I was dreading that. Took it to the shop, and you nailed it. Auxiliary battery was shot. 330€ later and the Kuga's no longer having an existential crisis. Thanks for the input; appreciate it!