Open the key fob, remove the battery and look and see what size it is.
look in the owners manual
Open the key fob up and look see what battery it contains. Buy that exact battery.
Open the fob. Remove the battery Use a pencil eraser to clean the battery contacts Use pencil eraser to clean the switch contacts on the printed circuit board (they look like interleaved fingers typically) replace the battery with a fresh one. If that doesn't work, buy a new FOB.
look in your owners manual and if nothing in there you will have to let the dealer do it.
Free On Board (FOB)
fob
I have a Toyota, and my key fob light stayed on also. I called the dealer, and they said the button on the fob was stuck down INSIDE the fob. So, I simply unscrewed the screw on the back of the fob, opened the fob, then put it back together. The fob was fixed. I didn't have to fix anything in the fob.
the key fob battery is the battey in a key fob torch
Fob stands for Fresh Of The Boat. FOB is a term for a new person in the country that stands out
Open it up and look see.
the fob may need recoding to the vehicle, if you still have the second fob then point and operate this fob at the receiver (by the interior mirror) and operate the faulty fob at the same time, this should bring the second fob back into sinc. robb