A4 Key Fob Dead: DIY Fix vs. Mechanic Visit

Had the same issue on my 2018 A3 2.0 TFSI. The key fob started acting up with inconsistent unlocking and error messages on the dash. Initially thought it was a serious electronic issue, but it turned out to be just a low battery in the key. Changed the battery myself using a CR2032 cell. The whole process took about 5 minutes with a small flathead screwdriver. After battery replacement, the keyless entry system worked perfectly again. The warning messages disappeared immediately after starting the car. Important note: If your key fob still doesnt work after a battery replacement, there could be contact issues inside the key. Sometimes moisture can corrode the battery contacts, but this is quite rare on newer Audi keys. The key fob usually gives early warning signs of low voltage, like reduced range or requiring multiple presses to work. Best to replace the battery as soon as you notice these symptoms to avoid getting completely locked out. For reference, dealer diagnostic checks later confirmed it was only the dead key battery causing all symptoms. No programming or additional repairs were needed.

Thanks for sharing that experience. Really helpful as Im dealing with pretty much the exact same symptoms on my A4. The reduced range has been noticeable for a while now, but I kept putting off the auto key battery replacement. Just curious, would you remember roughly how much you paid for the CR2032 battery? Also, has everything been working fine since the key fob battery swap, or have you noticed any other electrical quirks?

Actually went to the mechanic instead of DIY route since I was due for service anyway. The battery replacement for the key fob cost 37 Euro total, bit pricier than buying just the CR2032 cell, but they checked all connections and cleaned the contacts too. Everything has been working flawlessly since the low battery warning was fixed. No more error messages, keyless entry works every time, and the range is back to normal. The battery replacement completely resolved all the symptoms, no electrical issues or quirks at all. If you are seeing reduced range and getting warnings, its definitely worth fixing soon. A low voltage key fob can eventually stop working completely, which could leave you stranded. The whole process at the shop took less than 15 minutes. The mechanic mentioned they see this issue often on A4 models around the 2-3 year mark, so your timeline fits perfectly with the typical key battery lifespan.

Thanks for the advice. Took it to my regular shop yesterday and turns out you were right, just needed a new key fob battery. Total bill was 42 Euro which included a quick system check. The mechanic showed me the old battery and it was completely drained. He mentioned these electronic keys typically need a battery swap every couple years, so I probably should have dealt with it sooner when I first noticed the reduced range. Everything is working perfectly now, no more error messages and the keyless entry is responsive again. The whole visit took about 20 minutes, most of which was them doing a courtesy check of other systems while they had it hooked up. Good to know for next time that this is a common issue and not something more serious. Will definitely pay attention to those early warning signs of a dying key battery in the future rather than waiting until it almost completely fails.