Avensis key battery low warning

The symptoms you are experiencing indeed suggest the electronic key's battery may be depleted. Has the vehicle's mileage exceeded the typical lifespan of the factory-installed battery? Have you attempted to use the physical key to verify central locking functionality?

Mileage is at 187122 km. I haven't tried the physical key yet, but I was hoping it was just the battery. Is it likely to be something more serious than that?

Considering the vehicle's mileage, it is highly probable that the key fob battery requires replacement. Although alternative causes exist, such as receiver malfunction, commencing with the battery replacement is judicious. Should the issue persist, diagnostic evaluation by a qualified technician is advisable.

Thanks for the advice! I replaced the key fob battery (cost me about 37€) and everything is working perfectly again. Really appreciate the help!