Page 2 of 430

Four-Wheel Drive
.................................. 312
Front Axle
............................................ 313
Noise Control System
........................... 314
Bulb Replacement
................................ 315
Windshield Wiper Blade Replacement
... 316
Other Service Items
.............................. 317
Tires
..................................................... 321
Appearance Care
.................................. 331
Vehicle Identification
............................. 340
Electrical System
.................................. 340
Capacities and Specifications
................ 347
Normal Maintenance
Replacement Parts
............................ 352Maintenance Schedule
.............................. 359
Maintenance Schedule
.......................... 360
Customer Assistance Information
............. 403
Customer Assistance and Information
... 404
Reporting Safety Defects
...................... 414
Index
.......................................................... 417
2
Page 175 of 430

Oil Pressure Gage
The engine oil pressure gage, on the lower right
portion of your instrument panel cluster, shows
engine oil pressure in psi (pounds per square inch)
or in kPa (kilopascals). Oil pressure may vary
with outside temperature and oil viscosity,
but readings of 30 to 40 psi (205 to 275 kPa) on
gasoline engines at operating temperature
and moderate road speeds are normal. If you
have a diesel engine, the normal operating range
should be between 35 and 70 psi (240 to 480 kPa).A reading in the low pressure zone may be
caused by a dangerously low oil level or other
problem.
If you have a Caterpillar
®diesel engine, also see
your Caterpillar®Operation & Maintenance
Manual.
{CAUTION:
Do not keep driving if the oil pressure is
low. If you do, your engine can become so
hot that it catches re. You or others
could be burned. Check your oil as soon
as possible and have your vehicle
serviced.
Notice:Lack of proper engine oil maintenance
may damage the engine. The repairs would
not be covered by your warranty. Always follow
the maintenance schedule in this manual for
changing engine oil.
United StatesCanada
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Page 176 of 430

Low Oil Level Light
Your vehicle may have
a low oil level light.
This light should come on as a check, when you
start your engine. If the light fails to come on, have
it repaired as soon as possible so you will be
aware when the oil level is low.
Vehicles that have Caterpillar
®diesel engines may
not have a low oil level light. In this case, the light
will neither come on as a check when you start your
engine, nor will it come on to indicate a low oil level.
If this light comes on and stays on, it means your
engine is low on oil. You need to check the oil level
right away. SeeEngine Oil (Caterpillar
®DieselEngine) on page 268orEngine Oil (Gasoline
Engine) on page 268orEngine Oil (DURAMAX
®/
Isuzu Diesel Engine) on page 272for further
information.
Notice:Lack of proper engine oil maintenance
may damage the engine. The repairs would
not be covered by your warranty. Always follow
the maintenance schedule in this manual for
changing engine oil.
Change Engine Oil Light
The change engine oil
light should come on
briefly as a bulb
check when you start
the engine. If the
light does not come on,
have it serviced.
If the change engine oil light comes on and stays
on after you start the engine, have the oil
changed.
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Page 276 of 430

GM Goodwrench®oil of the recommended
viscosity grades meets all the requirements for
your vehicle.
Engine Oil Additives
Do not add anything to the oil. The recommended
oils with the API service symbol are all you will
need for good performance and engine protection.
When to Change Engine Oil (Vehicles
Without the Engine Oil Life System)
If you have the 6.6L V8 DURAMAX®Engine:
Change engine oil and filter every 15,000 miles
(24 000 km), or every 12 months, or every
750 hours of engine operation, whichever occurs
first. If you have the Isuzu 6H Engine: Change
engine oil and filter every 12,000 miles
(20 000 km), or every 12 months, or every
600 hours of engine operation, whichever occurs
first. SeeScheduled Maintenance on page 363.
Engine Oil Life System
(Gasoline Engine)
When to Change Engine Oil
Your vehicle has a computer system that lets you
know when to change the engine oil and filter.
This is based on engine revolutions and engine
temperature, and not on mileage. Based on driving
conditions, the mileage at which an oil change
will be indicated can vary considerably. For the oil
life system to work properly, you must reset the
system every time the oil is changed.
When the system has calculated that oil life has
been diminished, it will indicate that an oil change is
necessary. A change engine oil light will come on.
SeeChange Engine Oil Light on page 176. Change
your oil as soon as possible within the next
600 miles (1 000 km). It is possible that, if you are
driving under the best conditions, the oil life system
may not indicate that an oil change is necessary for
over a year. However, your engine oil and filter
must be changed at least once a year and at this
time the system must be reset. Your dealer has
GM-trained service people who will perform this
work using genuine GM parts and reset the system.
It is also important to check your oil regularly and
keep it at the proper level.
276
Page 295 of 430

Power Steering Fluid
SeeScheduled Maintenance on page 363to
determine when to check your power steering fluid.
How To Check Power Steering Fluid
Check your power steering fluid only when the
engine is warm. If the engine is not warm, you
probably will not get an accurate reading.
If the fluid level is between the MIN (Minimum) and
MAX (Maximum) marks, you have enough. If you
need fluid, add only enough of the proper fluid to
bring it in between the MIN and MAX marks.
If your power steering fluid level is low, this can
cause the brake or service brakes soon warning
lights to come on. In addition, the steering
effort and emergency brake distance could
increase.If either light remains on after you have added
power steering fluid to the proper level, then shut
off the engine for 10 seconds. This should
reset the brake warning lights. If one or both lights
stay on, see “Hydraulic Brake System Warning
Lights” underBrake System Warning Light
on page 169for more information.
What to Use
To determine what kind of fluid to use, see
Part C: Recommended Fluids and Lubricants on
page 397.
Notice:When adding power steering uid or
making a complete uid change, always
use the proper uid. Failure to use the proper
uid can cause leaks and damage hoses
and seals.
295
Page 301 of 430

Electric Air Compressor
Your vehicle may have an electric air compressor.
This compressor is used to run options that
require pressurized air, such as an air horn, air
seat, 7.8L engine exhaust restrictor, or 7.8L engine
exhaust brake.
The air compressor is used when vehicles do not
have an air brake system.
The air supply for
this system must be
maintained by releasing
the drain valve to eject
any moisture that
may have built up in
the system.
It is recommended that this system be drained on
a weekly basis.
Clutch Pedal Free Travel
If you have a V8 engine and a manual
transmission, the clutch will need adjustment
when pedal free travel gets down to about 1/4 inch
(6 mm), as measured at the clutch pedal pad.
You should have 1 1/2 to 2 inches (38 to 51 mm)
of clutch pedal free travel.
If the clutch ever needs service, be sure to use
only GM clutch replacement parts.
Chassis Lubrication
Your Maintenance Schedule provides all of the
required chassis lubrication intervals and identifies
proper lubricants to use. Be sure to see the
Maintenance Schedule before performing any
chassis lubrication service. To determine location of
chassis lubrication items, use the following charts.
301
Page 317 of 430

Other Service Items
Fuel Filter
Fuel Filter/Pressure Regulator
(Gasoline Engines)
The steel fuel filter/pressure regulator is located
near the engine compartment on the driver’s
side frame rail. If your vehicle has a rear steel fuel
tank, the fuel filter/pressure regulator is located
near the rear fuel tank, on the driver’s side frame
rail. SeeScheduled Maintenance on page 363
for recommended service intervals.
If your vehicle is equipped with the optional Davco
spin-on type filter, it is located on the driver’s
side frame rail.
Fuel Filter (Diesel Engines)
If you have a diesel engine, your fuel filter is
located in the engine compartment on the driver’s
side of the vehicle, or along the driver’s side
frame rail. See “Fuel Filter Replacement” earlier in
this section for further information.
Also seeScheduled Maintenance on page 363for
recommended service intervals.
Primary Fuel Filter and Water
Separator
If you have a diesel
engine, you may have
this spin-on filter. It
is located on the driver’s
side frame rail.
It has a clear plastic drain bowl at the bottom.
Check the drain bowl occasionally for any water or
particles.
To drain the bowl, do the following:
1. Shut off the engine.
2. Partially open the drain valve at the bottom of
the filter.
SeeEngine Oil (Caterpillar
®Diesel Engine) on
page 268orEngine Oil (Gasoline Engine) on
page 268orEngine Oil (DURAMAX
®/Isuzu Diesel
Engine) on page 272for proper disposal
procedures.
317
Page 328 of 430

How Often to Check
Wheel tightness is so important you should have a
technician check 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. Be sure
to repeat this service whenever you have a tire
removed or serviced. SeeScheduled Maintenance
on page 363for further information.
Wheel Replacement
Replace any wheel that is bent, cracked or badly
rusted or corroded. If wheel nuts keep coming
loose, replace the wheel. If the wheel leaks
air, replace it.
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:
A leaking wheel could fail without warning.
A wheel designed for tubeless tires could
be leaking because it is damaged. Do not
use an inner tube or some other thing to try
to stop the leaking. Get a new wheel of the
proper type.
328