remove key and pry open with small screw driver the remove and replace battery a cr2032 i believe.How long have you had it?
I have had mine for about a year and it's still working. They also gave me a backup key incase something happened so
I wouldn't have to use the regular key.
I'd take it Down to the dealer and have them replace the battery or you could so it yourself. I'm not sure how to open up the ikey though.