I just replaced both my key batteries with new CR1616 Lithium.
Vehicle is 2010 yet the spare unused key battery failed. It still measured 3.0V which, is plenty, but no workie. I hooked up a variable PSU @3v and tested the remote ...worked ok but not on battery which is real odd! Usually Lithium battery voltage is a good indication of the capacity left in the battery but in this case...not! Replacing the battery fixed the issue.

edit:
Even with bad key fob battery I could use the key to open and start the vehicle though.