The Toyota version of the Pathfinder is the 4Runner - a much better vehicle.
To find a parasitic battery drain that drains the battery every 6 months is difficult to find without a multi-meter.
With everything shut off, you would need to take out each fuse one-by-one and check with the milli-amp selection on the multi-meter. See if there is any flow through the fuse. Be careful to connect the positive lead to the battery side of the fuse and the negative lead to the output side of the fuse.
If you methodically go through every fuse, you will find the small drain. (It could be the security system.)
Good luck.
