Buick 2005 Century Owner's Manual page 272

The system normally takes 15 to 20 minutes of driving
time in each of three speed ranges to determine
tire pressures. The speed ranges are 15 to 40 mph
(25 to 65 km/h), 40 to 65 mph (65 to 105 km/h)
and above 65 mph (105 km/h). When the storage of the
tire inflation information is complete, the LOW TIRE
light will come on the instrument panel after two to
eight minutes if one tire is inflated 12 psi (83 kPa) less
than the other three tires. Detection thresholds may
be higher and detection times may be longer on rough
roads, curves and at high speeds. The system is
not capable of inflation differences at speeds greater
than 70 mph (110 km/h).
The tire inflation monitor system will not alert you if the
pressure in more than one tire is low, if the system
is not properly calibrated, or if the vehicle is moving
faster than 70 mph (110 km/h).
The LOW TIRE light will stay on while the ignition is on,
until the system is reset.
5-62
Do not reset the tire inflation monitor system without
first correcting the cause of the problem and checking
and adjusting the pressure in all four tires. If the
system is reset when the tire pressures are incorrect,
it will not function properly and may not alert you when a
tire is low.
Any time a tire's pressure is adjusted, the tires are
rotated, or one or more tires is repaired or replaced,
the tire inflation monitor system will need to be
reset. The system also needs to be reset when new
tires are purchased and if the vehicle's battery has
been disconnected.
To reset the system, do the following:
1. Turn the ignition to RUN.
2. Remove the passenger's side instrument panel
cover to access the fuse block.
3. Press and hold the RESET button in the fuse block
for about five seconds.
The LOW TIRE light will come on and flash three
times. Then it will go off. If the light does not go off,
see your dealer for service.