Toyota 2008 Corolla Owner's Manual page 306

'08 Corolla_U (L/O 0706)
Leak detection pump
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 trunk for several minutes. It does not indicate a
malfunction.
Perchlorate Material
Special handling may apply,
See www.dtsc.ca.gov/hazardouswaste/perchlorate.
Your vehicle has components that may contain perchlorate.
These components may include airbag, seat belt preten-
sioners, and wireless remote control batteries.
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2008 COROLLA from Aug. '07 Prod. (OM12B28U)