From page 9 in the owners manual.
Noise from under the vehicle S00AK01
NOTE
You may hear a noise from under the
vehicle approximately 5 to 10 hours
after the ignition switch is turned to the
“LOCK”/“OFF” position. However, this
does not indicate a malfunction. This
noise is caused by the operation of the
fuel evaporation leakage checking system
and the operation is normal. The
noise will stop after approximately 15
minutes.