Check by the gas tank for rust. Take magnet to the back of the rear wheels. Look for rust along the drivers seat and base of pillar, and check the tailgate for operation and see if the gauges work.
They are known and prone to rust and corosion in those areas. They are also common to electrical probs in the instrument panel.
if you get it i would disconnect the amp meter. They short out and burn the board.
I personally love FSJ's.