Tire Pressure Monitor System - GMC 2008 Envoy Denali Owner's Manual

If your vehicle has P255/50R20 104V size tires installed
on the rear axle, they will require inflation pressure
adjustment when driving your vehicle at speeds above
99 mph (160 km/h). Set the cold inflation pressure, for
the rear tires only, to the maximum inflation pressure
shown on the tire sidewall, or 38 psi (262 kPa), whichever
is lower. See the example following. When you end this
high-speed driving, return the tires to the cold tire inflation
pressure shown on the Tire and Loading Information
label. See Loading Your Vehicle on page 4-34.
Example:
You will find the maximum load and inflation pressure
molded on the tire's sidewall, in small letters, near
the rim flange. It will read something like this: Maximum
load 690 kg (1521 lbs) 300 kPa (44 psi) Max. Press.
For this example, you would set the inflation pressure for
high-speed driving at 38 psi (262 kPa).
The inflation pressure for the front tires should be set to
the cold tire inflation pressure shown on the Tire and
Loading Information label.
Racing or other competitive driving may affect the
warranty coverage of your vehicle. See your warranty
booklet for more information.

Tire Pressure Monitor System

The Tire Pressure Monitor System (TPMS) uses radio
and sensor technology to check tire pressure levels. The
TPMS sensors monitor the air pressure in your vehicle's
tires and transmit tire pressure readings to a receiver
located in the vehicle.
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.)
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.
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.
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