Audi A6 Alarm Failure Traced to Auxiliary Battery

Had a similar battery problem with my Audi A4 TDI 2013. With moderate experience working on cars, I first noticed the system diagnosis errors popping up out of nowhere, followed by the alarm system failing completely. After initial attempts to resolve the battery signal issues myself, I took it to a workshop. They confirmed the auxiliary battery was degraded due to age, which is a common issue in these models after 8-10 years. The complete fix included: Battery system diagnosis, Replacement of auxiliary alarm system battery, System reset and recalibration, Testing of all affected components Total cost was 330 Euro, including parts and labor. The repair solved both the system errors and restored full alarm functionality. To provide more specific advice for your case, could you share: Current battery voltage readings, Age of the current auxiliary battery, Any other electrical issues you noticed, Whether you see any other warning lights, If the main battery has been replaced recently These details would help determine if your situation matches what I experienced with my A4.

I need to share that my mileage is 121516 KM, last serviced 3 months ago. Thanks for sharing your A4 experience. The electrical issue matches my symptoms exactly. After checking with a multimeter, my auxiliary battery shows 11.2V, which confirms a battery problem. The main car battery was replaced last year and tests fine at 12.6V. The auxiliary battery is original from 2011, so replacement seems the logical next step. No other warning lights are present besides the system diagnosis error. The battery signal appears normal when starting the car, but drops significantly after a few hours of parking. Your repair costs seem reasonable. Planning to book a workshop appointment to get this resolved properly with a full battery check and system reset.

Thanks for those details, your voltage readings confirm what I experienced with my A4. The 11.2V on the auxiliary battery is definitely below the required threshold, matching the same pattern I saw before my repair. The battery signal behavior you described, dropping after parking, was exactly my issue too. My system diagnosis also showed similar symptoms before the complete fix. Since your auxiliary battery is original from 2011, its definitely reached end-of-life, just like mine did. The workshop actually told me these auxiliary batteries typically last 8-10 years, so your timeline fits perfectly. Good call on booking a proper workshop appointment. Make sure they perform a complete battery system diagnosis, in my case, they found some minor corrosion on the connections that needed cleaning during the repair process. Based on your mileage and service history, I expect your repair costs should be close to what I paid (330 Euro). The system reset and recalibration after the auxiliary battery replacement is crucial, skipping this step can lead to persistent alarm system issues.

Thanks for the detailed responses and voltage information. Your explanation of the battery signal behavior really helped confirm my suspicions. The electrical issue symptoms you described match my situation perfectly. My 11.2V auxiliary battery reading and the age of the original 2011 battery definitely point to a battery problem requiring replacement. The system diagnosis error makes more sense now, especially with the voltage drop after parking. Will proceed with booking the workshop appointment for a complete battery check and replacement. The 330 Euro cost estimate seems fair for the full service including system reset and calibration. Given that my main battery is good at 12.6V, I feel confident this auxiliary battery replacement will resolve the alarm system issues. Just need to schedule a free slot at the workshop now that I know exactly what needs fixing. Helpful to know about checking for corrosion during the repair too. Will make sure they do the full system diagnosis and proper reset procedure.