VW Eos Alarm System Failure: Common Sensor Issues

Having some experience with VW vehicles, I encountered a similar security alarm issue on my 2011 VW Golf TDI. The immobilizer and alarm control unit started acting erratically, causing false alarm triggers and eventually a complete system failure. Initially thought it was a power failure in the central locking system, but the workshop diagnosed it as a programming issue. The alarm control module needed recoding to properly activate the optical locking signals through the indicators. The fix was relatively straightforward, they performed a software update and recoded the system settings. Total cost was 45€ for the diagnostic and reprogramming work. Since then, no more alarm-related problems. To better assist with your specific case, could you share: Are there any other electrical issues present? Does the remote key still work normally? When did the security alarm stop functioning? Have you noticed any warning lights on the dashboard? These details would help determine if your EOS is experiencing the same fault as my Golf did, as they share similar alarm system architecture from that production period.

Thanks for sharing your experience. My latest service was done at 89000km, just a few months ago. Actually, the issue started right after that service. The remote key works fine for locking/unlocking, but the alarm system remains completely inactive, no chirp, no lights flashing. No other electrical problems or warning lights are visible on the dashboard. The battery warning showed up briefly last week but disappeared after a short drive. Given the timing after the service, I wonder if this could be related to a battery issue or if something got disconnected during maintenance work.

Thanks for those additional details. Your symptoms match exactly what I experienced with my Golf, the alarm system died right after routine maintenance too. However, unlike your case, my remote locking completely failed. The temporary battery warning you mentioned is significant. In VW models from this era, a weak battery can cause the alarm sensor and immobilizer systems to behave erratically. When the battery voltage drops below a certain threshold, the security alarm system often shuts down to preserve power for essential functions. Since your issue started post-service, I would: 1. Have the battery tested, could be nearing end of life 2. Check if any security alarm connections were accidentally disturbed during service 3. Get the battery voltage measured while the car is running My Golf needed both a new battery and a reset of the alarm control module to resolve the issue completely. The total repair came to 180€, 120€ for the battery and 60€ for the system reset and testing. Before heading to the shop, try disconnecting your battery for about 15 minutes. This basic reset sometimes resolves security alarm glitches in these VW models. Just be ready to input your radio code afterward.

Thanks for the detailed information. What you described makes perfect sense, especially the part about disconnecting the battery. I will try that reset procedure first before spending money at the shop. The timing of my battery warning light certainly suggests the battery could be the culprit. Since my vehicle has the original battery from 2013, it is probably due for replacement anyway. A failing battery causing anti-theft system issues would explain both the alarm sensor malfunction and that brief warning light. I will get the battery tested and voltage checked first. If that does not resolve the security alarm problem, I will have them check for loose connections from the recent service. The total repair cost you mentioned seems reasonable if I end up needing both a new battery and alarm system reset. Will report back after trying these steps. Really appreciate you sharing your similar experience with the VW alarm system issues.