Audi Key Fob Issues: Simple Battery Fix vs System Fault

I had a very similar issue with my 2012 Audi S4, and with some basic experience working on cars, I can share what worked for me. The symptoms you describe match exactly what I experienced, inconsistent locking, unreliable keyless entry, and warning messages about low voltage in the electronic key. The fob battery replacement completely resolved these issues. I visited a workshop where they diagnosed it within minutes. The total cost was 37 Euro, which covered both the new battery and installation. They used a CR2032 battery, which is common for many Audi key fobs. Before you proceed, could you confirm: Do you get any other warning messages on the dashboard? How long have you owned the key fob? Have you noticed if the issues are worse in cold weather? This information would help determine if your symptoms truly match what I experienced or if there might be additional factors to consider. In most cases, when the key battery gets low, these exact symptoms appear, and a simple battery replacement fixes everything. The workshop also mentioned its good practice to replace the fob battery every 2-3 years as preventive maintenance, even before problems start showing up.

Thanks for confirming. My S5 has 135672 KM and the last service was done 3 months ago. No other warning messages appear on the dashboard besides the low battery alert. The dead key fob symptoms started about 2 weeks ago. The original electronic key came with the car when I bought it used 3 years ago, so I have no record of the last battery change. The weather has been consistent lately, so I cannot confirm if temperature affects the low voltage issues. Just worried about getting stranded somewhere with a completely dead key if I wait too long to address this. A 37 Euro fix sounds reasonable if that solves it. Will try the battery replacement first before exploring other potential causes.

Good to hear back from you. Based on the timing and symptoms you describe, this definitely matches my experience with the key battery issue. Since youve had the electronic key for 3 years without a known battery change, its right on schedule for replacement. The fact that you only see the low battery warning without other error messages is a good sign. When my car key started acting up, I also worried about getting stranded, but the key fob has a backup physical key inside for emergencies. One tip from my experience: even if the keyless entry stops working completely due to low voltage, you can still start the car by holding the dead key fob directly against the steering column. This emergency feature worked on my S4 and should work the same on your S5. Your mileage and service history suggest the issue is isolated to the key battery rather than a more complex electrical problem. The basic battery replacement should resolve the inconsistent locking and unreliable keyless access, just like it did in my case. Would you like details on how to access the backup physical key in case the electronic key dies completely before you get the battery replaced?

Thanks for the detailed advice. No need to explain the backup key, I actually found that hidden feature when I first got the car, so I know where it is if needed. The emergency start method you mentioned is especially good to know. I was not aware the fob could still work by holding it against the steering column when the battery gets too low for keyless operation. Given that my symptoms match what you experienced, and considering the key fob is likely still on its original battery after 3 years, I will go ahead with the battery replacement tomorrow. The 37 Euro cost is much better than risking a complete failure or dealing with a more expensive electrical diagnosis. I appreciate you confirming that the low voltage warning without other error messages typically points to a simple fob battery issue. This has given me confidence to try the basic fix first before worrying about bigger problems with the keyless system.