After refueling, turn the fuel tank cap until you hear a click. Once the cap is released, it will turn slightly in the opposite direction.

Caution
When replacing the fuel tank cap
Do not use anything but a genuine toyota fuel tank cap designed for your vehicle. Doing so may cause a fire or other incident which may result in death or serious injury.
Opening the fuel tank capAir conditioning control assembly (for automatic air conditioning system)
Components
Removal
Disconnect cable from negative battery
terminal
Notice:
Wait at least 90 seconds after disconnecting the
cable from the negative (-) battery terminal to
prevent airbag and seat belt pretensioner activation.
Remove no. 2 Instrument cluster finish
panel center ...
Terminals of ecu
Check combination meter assembly
Measure the voltage and resistance of the
connector.
Check instrument panel junction block (main body ecu)
Measure the voltage and resistance of the
connectors.
...
If a warning light turns on or
a warning buzzer sounds
Calmly perform the following actions if any of the warning
lights comes on or flashes. If a light comes on or flashes, but
then goes off, this does not necessarily indicate a malfunction
in the system. However, if this continues to occur, have
the vehicle inspected by your Toyota dealer.
Actions to ...