gas tank problem

If you mean that it is hard to fill your tank, then that is usually caused by a saturated or defective evaporative carbon canister and vent valve. You may also have a check engine light on with a code P0446, which indicates a problem with the above assembly. Need to replace these as a unit, they go out a lot on Toyota, if you try to fill up after the nozzle first clicks off. This is called 'topping off' and it ruins these components over time.