2003 XLS Avalon clicking under hood

[iluvavalons]

the EFI relay is clicking under the hood unless I put the key in the ignition( don't have to turn the key which has a computer chip in it) or remove a fuse or the relay. I was told it could be the battery, but had it checked and had a mechanic check it out for 3 - 4 hours and couldn't find out what was wrong. Could it have to do with the security system?