Page 141 of 374

Engine Road Speed Governor
This system controls maximum vehicle speed
automatically and reduces engine power until vehicle
speed gets down to maximum governed speed.
The default setting for C4500 and C5500 models up to
19,500 lbs GVWR is 80 to 85 mph (128 to 136 km/h).
Most other models have a default setting of 75 mph
(120 km/h), although some tire sizes and tread patterns
may limit maximum speed to 55 to 65 mph
(86 to 105 km/h). You may have a label on the headliner
of your vehicle with more information on your engine road
speed governor. See your GM dealer for assistance with
programming your engine limited speed.
Safety Belt Reminder Light
When the key is turned to RUN or START, a light will
come on for several seconds to remind people to fasten
their safety belts.
The safety belt light will
also come on and stay on
for several seconds.
Safety Belt Reminder Tone
If your vehicle has this feature, when you turn your key
to RUN or START, a tone will sound for several
seconds to remind people to fasten their safety belts.
Airbag Readiness Light
If your vehicle has airbags, there is an airbag readiness
light on the instrument panel, which shows the airbag
symbol. The system checks the airbag’s electrical
system for malfunctions. The light tells you if there is an
electrical problem. The system check includes the
airbag sensors, the airbag modules, the wiring, the
passenger airbag suppression circuit and the crash
sensing and diagnostic module. For more information on
the airbag system, seeAirbag System on page 1-48.
This light will come on
when you start your
vehicle, and it will flash for
a few seconds. Then the
light should go out. This
means the system is ready.
3-27
Page 206 of 374
Loading Your Vehicle
There is a vehicle specific GVW Rating label on your
vehicle that shows how much weight it may properly
carry. It also shows the size of your original tires and the
inflation pressures needed to obtain the gross weight
capacity of your vehicle. This is called the Gross Vehicle
Weight Rating (GVWR).
The GVWR includes the weight of the vehicle, all
occupants, fuel and cargo.The GVW Rating label is provided by the final
manufacturer and should be on the door or door jamb.
It also tells you the maximum weights for the front
and rear axles, called Gross Axle Weight Rating
(GAWR). To find out the actual loads on your front and
rear axles, you need to go to a weigh station and
weigh your vehicle. Your dealer can help you with this.
Be sure to spread out your load equally on both
sides of the center line.
Never exceed the GVWR for your vehicle, or the GAWR
for either the front or rear axle.
And, if you do have a heavy load, you should spread
it out.
4-32
Page 284 of 374

Dual Tire Operation
When the vehicle is new, check the wheel nut tightness
on all wheels with a torque wrench after your first
100 miles (160 km) and then 1,000 miles (1 600 km) after
that. Whenever a wheel, wheel bolt or wheel nut is
removed or serviced, repeat the 100 miles (160 km), and
then 1,000 mile (1 600 km) wheel nut tightness check.
SeeTightening the Wheel Nuts on page 5-73for wheel
nut tightening information and proper torque values.
{CAUTION:
If you operate your vehicle with a tire that is
badly underin ated, the tire can overheat. An
overheated tire can lose air suddenly or catch
re. You or others could be injured. Be sure all
tires (including the spare, if any) are properly
in ated.
SeeTires on page 5-70andIn ation - Tire Pressure on
page 5-71for more information on proper tire inflation.
When It Is Time for New Tires
Replace your tires when the tread depth is down to
1/8 of an inch (3.2 mm) for the front tires, or 1/16 of an
inch (1.6 mm) for a rear tire. Also, you need a new
tire if:
•You can see cord or fabric showing through the
tire’s rubber.
•The tread or sidewall is cracked, cut or snagged
deep enough to show cord or fabric.
•The tire has a bump, bulge or split.
•The tire has a puncture, cut or other damage that
can’t be repaired well because of the size or
location of the damage.
{CAUTION:
Mixing tires could cause you to lose control
while driving. If you mix tires of different
types — like radial and bias-belted tires — the
vehicle may not handle properly, and you
could have a crash. Be sure to use the same
type of tires all around.
5-72
Page 285 of 374

When you replace tires, make sure they are the same
size, load range, speed rating and construction type
(bias, bias-belted or radial) as your original tires.
If your vehicle has four-wheel drive, the axle differentials,
propshafts and transfer case may be damaged if tires
of different sizes, brands or tread types are installed on
the front and rear axles. That damage would not be
covered under your warranty.
Wheel Alignment and Tire Balance
The wheels on your vehicle were aligned at the
factory to give you the longest tire life and best overall
performance.
Proper front wheel alignment must be maintained in
order to ensure efficient steering, good directional
stability, and prevent abnormal tire wear. If you notice
unusual tire wear or your vehicle is pulling one way
or the other, the alignment may need to be reset. If you
notice your vehicle vibrating when driving on a smooth
road, your wheels may need to be balanced.
Tightening the Wheel Nuts
{CAUTION:
Wheel nuts that are not tight can work loose. If
all the nuts on a wheel come off, the wheel can
come off the vehicle, causing a crash. All
wheel nuts must be properly tightened. Follow
the rules in this section to be sure they are.
This section lets you know how often to check the
tightness of the wheel nuts on your vehicle and how tight
they must be.
5-73