Page 356 of 452

(A) Light Truck (LT-Metric) Tire:The United States
version of a metric tire sizing system. The letter ªLTº as
the ®rst two characters in the tire size means a light
truck tire engineered to standards set by the U. S. Tire
and Rim Association.
(B) Tire Width:The three-digit number indicates the
tire section width in millimeters from sidewall to sidewall.
(C) Aspect Ratio:A two-digit number that indicates
the tire height-to-width measurements. For example, if
the tire size aspect ratio is ª75,º as shown in item ªCº of
the illustration, it would mean that the tire's sidewall is
75% as high as it is wide.(D) Construction Code:A letter code is used to
indicate the type of ply construction in the tire. The
letter ªRº means radial ply construction; the letter ªDº
means diagonal or bias ply construction; and the
letter ªBº means belted-bias ply construction.
(E) Rim Diameter:Diameter of the wheel in inches.
(F) Service Description:The service description
indicates the load range and speed rating of a tire.
The load index can range from 1 to 279. Speed ratings
range from ªAº to ªZº. The light truck tire size example
above shows dual or single tire con®gurations.Tire Terminology and De®nitions
Air Pressure:The amount of air inside the tire pressing
outward on each square inch of the tire. Air pressure
is expressed in pounds per square inch (psi) or
kilopascal (kPa).
Accessory Weight:This means the combined weight
of optional accessories. Some examples of optional
accessories are, automatic transmission, power steering,
power brakes, power windows, power seats, and air
conditioning.
Aspect Ratio:The relationship of a tire's height to
its width.
Belt:A rubber coated layer of cords that is located
between the plies and the tread. Cords may be made
from steel or other reinforcing materials. Light Truck (LT-Metric) Tire
5-64
Page 365 of 452

Wheel Replacement
Replace any wheel that is bent, cracked, or badly rusted
or corroded. If wheel nuts keep coming loose, the
wheel, wheel bolts and wheel nuts should be replaced.
If the wheel leaks air, replace it (except some
aluminum wheels, which can sometimes be repaired).
See your dealer if any of these conditions exist.
Your dealer will know the kind of wheel you need.
Each new wheel should have the same load-carrying
capacity, diameter, width, offset and be mounted
the same way as the one it replaces.
If you need to replace any of your wheels, wheel bolts
or wheel nuts, replace them only with new GM
original equipment parts. This way, you will be sure to
have the right wheel, wheel bolts and wheel nuts
for your vehicle.{CAUTION:
Using the wrong replacement wheels, wheel
bolts or wheel nuts on your vehicle can be
dangerous. It could affect the braking and
handling of your vehicle, make your tires lose
air and make you lose control. You could have
a collision in which you or others could be
injured. Always use the correct wheel, wheel
bolts and wheel nuts for replacement.
Notice:The wrong wheel can also cause problems
with bearing life, brake cooling, speedometer or
odometer calibration, headlamp aim, bumper height,
vehicle ground clearance and tire clearance to the
body and chassis.
See
Changing a Flat Tire on page 5-76for more
information.
5-73
Page 366 of 452

Used Replacement Wheels
{CAUTION:
Putting a used wheel on your vehicle is
dangerous. You can't know how it's been used
or how far it's been driven. It could fail
suddenly and cause a crash. If you have to
replace a wheel, use a new GM original
equipment wheel.
Tire Chains
{CAUTION:
Don't use tire chains. There's not enough
clearance. Tire chains used on a vehicle
without the proper amount of clearance can
cause damage to the brakes, suspension or
other vehicle parts. The area damaged by the
tire chains could cause you to lose control of
your vehicle and you or others may be injured
in a crash. Use another type of traction device
only if its manufacturer recommends it for use
on your vehicle and tire size combination and
road conditions. Follow that manufacturer's
instructions. To help avoid damage to your
vehicle, drive slowly, readjust or remove the
device if it's contacting your vehicle, and
don't spin your wheels. If you do ®nd traction
devices that will ®t, install them on the
rear tires.
5-74
Page 367 of 452

If a Tire Goes Flat
It's unusual for a tire to ªblowoutº while you're driving,
especially if you maintain your tires properly. If air goes
out of a tire, it's much more likely to leak out slowly.
But if you should ever have a ªblowout,º here are a few
tips about what to expect and what to do:
If a front tire fails, the ¯at tire will create a drag that
pulls the vehicle toward that side. Take your foot off the
accelerator pedal and grip the steering wheel ®rmly.
Steer to maintain lane position, and then gently brake to
a stop well out of the traffic lane.
A rear blowout, particularly on a curve, acts much like a
skid and may require the same correction you'd use
in a skid. In any rear blowout, remove your foot from the
accelerator pedal. Get the vehicle under control by
steering the way you want the vehicle to go. It may be
very bumpy and noisy, but you can still steer. Gently
brake to a stop, well off the road if possible.{CAUTION:
Lifting a vehicle and getting under it to do
maintenance or repairs is dangerous without
the appropriate safety equipment and training.
The jack provided with your vehicle is
designed only for changing a ¯at tire. If it is
used for anything else, you or others could be
badly injured or killed if the vehicle slips off
the jack. Use the jack provided with your
vehicle only for changing a ¯at tire.
If a tire goes ¯at, the next part shows how to use your
jacking equipment to change a ¯at tire safely.
5-75
Page 368 of 452
Changing a Flat Tire
If a tire goes ¯at, avoid further tire and wheel damage
by driving slowly to a level place. Turn on your
hazard warning ¯ashers.
{CAUTION:
Changing a tire can be dangerous. The vehicle
can slip off the jack and roll over or fall on you
or other people. You and they could be badly
injured or even killed. Find a level place to
change your tire. To help prevent the vehicle
from moving:
1. Set the parking brake ®rmly.
2. Put the shift lever in PARK (P).
3. Turn off the engine and do not restart
while the vehicle is raised.
4. Do not allow passengers to remain in the
vehicle.
CAUTION: (Continued)
CAUTION: (Continued)
5. Put the wheel blocks at the front and rear
of the tire farthest away from the one
being changed. That would be the tire on
the other side, at the opposite end of the
vehicle.
The following steps will tell you how to use the jack and
change a tire.
5-76
Page 379 of 452

{CAUTION:
Incorrect wheel nuts or improperly tightened
wheel nuts can cause the wheel to come loose
and even come off. This could lead to an
accident. Be sure to use the correct wheel
nuts. If you have to replace them, be sure to
get new GM original equipment wheel nuts.
Stop somewhere as soon as you can and have
the nuts tightened with a torque wrench to the
proper torque speci®cation. See ªCapacities
and Speci®cationsº in the Index for wheel nut
torque speci®cation.
Notice:Improperly tightened wheel nuts can lead
to brake pulsation and rotor damage. To avoid
expensive brake repairs, evenly tighten the wheel
nuts in the proper sequence and to the proper
torque speci®cation. See ªCapacities and
Speci®cationsº in the index for the wheel nut torque
speci®cation.
When you reinstall the regular wheel and tire, you must
also reinstall the center cap. Place the cap on the
wheel and tap it into place until it seats ¯ush with the
wheel. The cap only goes on one way. Be sure to line up
the tab on the center cap with the indentation on the
wheel.
5-87
Page 399 of 452

Fuses Usage
RR Wiper Not Used
SEO ACCYSpecial Equipment Option
Accessory
WS WPR Windshield Wipers
TBC ACCYTruck Body Controller
Accessory
IGN 3 Ignition, Heated Seats
4WDFour-Wheel Drive System,
Auxiliary Battery
HTR A/C Climate Control System
LOCK (Relay)Power Door Lock Relay
(Lock Function)
HVAC 1 Climate Control System
L DOORDriver's Door Harness
Connection
CRUISECruise Control, Power Take
Off (PTO)
UNLOCK (Relay)Power Door Lock Relay
(Unlock Function)
RR FOG LP Not Used
BRAKE Anti-Lock Brake System
DRIVER UNLOCKPower Door Lock Relay
(Driver's Door Unlock
Function)
IGN 0 TCMFuses Usage
TBC IGN 0 Truck Body Controller
VEH CHMSLVehicle and Trailer High
Mounted Stoplamp
LT TRLR ST/TRN Left Turn Signal/Stop Trailer
LT TRNLeft Turn Signals and
Sidemarkers
VEH STOPVehicle Stoplamps, Brake
Module, Electronic Throttle
Control Module
RT TRLR ST/TRN Right Turn Signal/Stop Trailer
RT TRNRight Turn Signals and
Sidemarkers
BODY Harness Connector
DDM Driver Door Module
AUX PWR 2 Not Used
LOCKS Power Door Lock System
ECC Not Used
TBC 2C Truck Body Controller
FLASH Flasher Module
CB LT DOORSLeft Power Windows Circuit
Breaker
TBC 2B Truck Body Controller
TBC 2A Truck Body Controller
5-107
Page 400 of 452
Center Instrument Panel Fuse Block
The center instrument panel utility block is located
underneath the instrument panel, to the left of the
steering column.
Device Usage
SEO Special Equipment Option
TRAILER Trailer Brake Wiring
UPFIT Up®tter (Not Used)
SL RIDERide Control Harness
Connection
HDLR 2 Headliner Wiring Connector
BODY Body Wiring Connector
DEFOG Rear Defogger Relay
HDLNR 1 Headliner Wiring Connector 1
SPARE RELAY Not Used
CB SEATDriver and Passenger Seat
Module Circuit Breaker
CB RT DOORRight Power Windows Circuit
Breaker
SPARE Not Used
INFOInfotainment Harness
Connection
5-108