I drove my 2013 XF to the local shopping center, got in to start car and it wouldn't start. After several attempts it stated smart key not detected, reposition key and press start button. I got out and the key worked to lock door but horn was very faint. I replaced battery and smart key and still nothing. I got an occasional ticking sound. I had the car tolled home and tried my second smart key and got the same message. I tried the whole placing the keys under the dash and next to the steering column but nothing worked. Anyone had this issue.

 

Which battery did you replace? In the key fob or in the car? Sounds like your car battery may be discharged or failing.