Chevrolet Impala 2007 Impala Owner's Manual page 364

The low tire pressure warning light may come on
in cool weather when the vehicle is first started,
and then turn off as you start to drive. This may be
an early indicator that the air pressure in the
tire(s) are getting low and need to be inflated to
the proper pressure.
Each tire, including the spare (if provided), should
be checked monthly when cold and inflated to
the inflation pressure recommended by the vehicle
manufacturer on the vehicle placard or tire
inflation pressure label. (If your vehicle has tires
of a different size than the size indicated on
the vehicle placard or tire inflation pressure label,
you should determine the proper tire inflation
pressure for those tires.)
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Accordingly, when the low tire pressure telltale
illuminates, you should stop and check your tires
as soon as possible, and inflate them to the
proper pressure. Driving on a significantly
under-inflated tire causes the tire to overheat and
can lead to tire failure. Under-inflation also
reduces fuel efficiency and tire tread life, and may
affect the vehicle's handling and stopping ability.
Please note that the TPMS is not a substitute for
proper tire maintenance, and it is the driver's
responsibility to maintain correct tire pressure, even
if under-inflation has not reached the level to trigger
illumination of the TPMS low tire pressure telltale.
As an added safety
feature, your vehicle
has been equipped
with a tire pressure
monitoring system
(TPMS) that illuminates
a low tire pressure
telltale when one
or more of your tires is
significantly
under-inflated.