i have a 91 sl and i had battery probems and i jump it and made so much other probems please do not jump it
The key battery for the ls400 is PN# br1216 www.lextechautomotivellc.com
According to the 2006 Ford Five Hundred Owner Guide : Each key fob takes ( 1 ) coin type three volt lithium battery ( CR2032 ) or equivalent
The Audi Key (with built in small light bulb) takes a PX625A battery
Open the key fob and remove the battery which has a # on it, and then buy a duplicate.
By using your key to unlock the door.
CR 2032
With the key inserted into the lock.
Open the key fob, remove the battery and look and see what size it is.
You can pull out the metal key that won't work in the trunk and then jump start the car from the battery.
Panasonic CR1618
cr2032
The battery size is CR2032. Pretty widely available at electronics stores