Audi A1 Anti-Theft System Failure Causes Alarm Issues

As an A4 2.0T owner from 2019, I experienced nearly identical symptoms. The immobilizer malfunction initially showed as a power failure in the alarm control module. This prevented the indicators from flashing during locking and the car alarm became unresponsive. The root cause was a faulty alarm control unit, which also affected the central locking system. The repair involved: Complete diagnostic scan, Removal and replacement of the alarm control module, Recoding of the immobilizer system, Programming new key synchronization The issue was relatively serious since it impacted multiple security systems. The car required specialized diagnostic equipment to properly reset the immobilizer after component replacement. Without proper repair, the system can trigger false alarms or fail to protect against theft. These symptoms are common across the newer Audi platforms, especially when the vehicle approaches 100000km. The original control module tends to fail due to voltage regulation issues. Best approach is having a full diagnostic scan done, as attempting partial fixes often leads to recurring alarm system failures.

Thanks for sharing those details about the A4 issue. I actually faced similar anti-theft system problems with my 2021 A1 last winter. The security alarm kept triggering out of nowhere and the immobilizer would sometimes prevent the car from starting. Turned out the battery issue was causing power failure to the control module, but initially the mechanics also suspected a faulty alarm unit. Would love to know what repair costs you ended up paying and if everything has worked properly since the fix. Having this information would really help when I talk to my mechanic about some recurring glitches I noticed recently.

Good news, since my last post, I got the A4's security alarm fully fixed. The fault turned out simpler than initially suspected. The immobilizer and alarm control issues were resolved by recoding the optical locking function. Total repair cost came to 45 Euro which covered diagnostic testing and system reprogramming. After months of use, the anti-theft system works flawlessly, indicators flash properly during locking, no more power failure warnings, and zero false alarms. The battery connection to the control module remains stable. This repair cost significantly less than replacing the entire alarm control unit, which was initially suggested. For recurring issues like yours, requesting a full system diagnostic first could save unnecessary parts replacement. The key is finding a shop with proper diagnostic tools to accurately identify if the immobilizer actually needs component replacement or just recoding. That initial assessment helps avoid overpaying for unneeded repairs.

Thanks everyone for the detailed responses. Just wanted to share how my situation turned out. Finally got my A1 checked last week and thankfully it was much simpler than expected. The anti-theft system malfunction stemmed from corroded connections in the alarm control module. The mechanic cleaned the contacts and recalibrated the immobilizer settings. Total bill came to 120 Euro, including diagnostic work and system reprogramming. No power failure warnings since then and the car alarm works perfectly now. The mechanic mentioned these connection issues are pretty common in newer models when moisture gets trapped near the control unit. Much better outcome than my previous repair attempts where they wanted to replace the entire alarm system. Definitely worth getting a second opinion when dealing with security system issues. Will keep monitoring for any recurring problems, but so far the fix seems solid. The central locking and immobilizer are responding normally again.