Toyota 2004 Highlander Owner's Manual page 8

'04 HIGHLANDER_U (L/O 0308)
Leak detection pump
(2AZ−FE engine)
This pump performs fuel evaporation leakage check. This
check is done approximately five hours after the engine is
turned off. So you may hear sound coming from under-
neath the luggage compartment for several minutes. It
does not indicate a malfunction.
viii
2004 HIGHLANDER from Aug. '03 Prod. (OM48478U)