Yesterday I went to start 2012 mustang. Had bright lights and battery was fully charged. Would not even try to turn over. I got to thinking that key has to have a battery. Snapped it open ,got a new battery at dollar store and solved problem. I'm going to carry a sparse 2 dollar better in glove box now.

 

wow thats weird. Those batteries should last for many years.

 

Now I gotta know, do all Mustangs have this battery in the key? I have an '09 and the key looks pretty well sealed to me.

 

YES They do

 

Are we talking the actual key or the remote in the fob?

 

in the fob

 

Thanks.

 

NP..