Car thinks there is a key inside???

How healthy is the 12v battery?

 

Has it always done that or did you just get the car? If the latter, the simplest explanation is that the previous owner dropped a fob in the car and its battery is still active. Does the car have the smart key? If so, leave the other fob far away and see if the car will start anyway when you push the start button. That should only happen if there is a fob somewhere in the car. Most likely locations are: wedged in next to one of the front seats, in one of the many storage slots in the center console, under the mats, in the glovebox, in the storage slots in the doors. If the car has a glasses holder near the front of the ceiling, look there too.

 

Doesn't the car beep when the fob battery is detected as getting weak? Maybe it's telling you to replace a $4 battery and not a $200 battery.

 

My wife had a similar problem when she rented a car from hertz. She could not get it to stay locked. She found the spare key fob in an envelope in the spare tire compartment. It had fallen out of it's silvered mylar envelope.

If the extra fob is near the diver's seat, it should start with the main fob 30 feet away. If the extra key is in the back seat or trunk it will not start.

 

I have gotten the ‘key detected in car’ message occasionally.
No idea why

 

maybe a funky ecu or connection