If this happened after a period of time in which the FJ was parked, be sure to check your fuel cap. Remove it and re-install it.
Just for fun, make sure your transfer case lever is truly engaged in 4x2 Hi by shifting it down and then back into 2 HI (in case that sensor is gettin' jiggy)
The Emissions control system does an evap control system self-check after the fuel tank cools off at night. This also explains the strange hummm of a vacuum pump running if you are ever sweeping the garage about 5 hours after getting home.
Good luck
