
When towing at high altitude on steep uphill grades,
consider the following: Engine coolant will boil at a lower
temperature than at normal altitudes. If you turn your
engine off immediately after towing at high altitude
on steep uphill grades, your vehicle may show signs
similar to engine overheating. To avoid this, let the
engine run while parked (preferably on level ground)
with the automatic transmission in PARK (P) for a
few minutes before turning the engine off. If you do get
the overheat warning, seeEngine Overheating on
page 5-24.
Parking on Hills
{CAUTION:
You really should not park your vehicle, with a
trailer attached, on a hill. If something goes
wrong, your rig could start to move. People
can be injured, and both your vehicle and the
trailer can be damaged.
But if you ever have to park your rig on a hill, here’s
how to do it:
1. Apply your regular brakes, but don’t shift into
PARK (P) yet. Then turn your wheels into the curb if
facing downhill or into traffic if facing uphill.2. Have someone place chocks under the
trailer wheels.
3. When the wheel chocks are in place, release the
regular brakes until the chocks absorb the load.
4. Reapply the regular brakes. Then apply your
parking brake and then shift to PARK (P).
5. Release the regular brakes.
When You Are Ready to Leave After
Parking on a Hill
1. Apply your regular brakes and hold the pedal down
while you:
•start your engine,
•shift into a gear, and
•release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store
the chocks.
4-50 

Maintenance When Trailer Towing
Your vehicle will need service more often when you’re
pulling a trailer. See the Maintenance Schedule for more
on this. Things that are especially important in trailer
operation are automatic transmission fluid (don’t overfill),
engine oil, axle lubricant, belt, cooling system and
brake system. Each of these is covered in this manual,
and the Index will help you find them quickly. If
you’re trailering, it’s a good idea to review these sections
before you start your trip.
Check periodically to see that all hitch nuts and bolts
are tight.
Trailer Wiring Harness
The optional heavy-duty trailer wiring package includes
a seven-wire harness assembly at the rear of the
vehicle and a four-wire harness assembly under the left
hand side of the instrument panel. The seven-wire
harness assembly is taped together and located in a
frame pocket at the driver side rear left corner of
the frame. The seven-wire harness includes a 30-amp
feed wire. Both harnesses come without connectors and
should be wired by a qualified electrical technician.
The technician can use the following color code chart
when connecting the wiring harness to your trailer
and trailer brake controller.Seven-Wire Harness
•Light Green: Back-up lamps
•Brown: Parking lamps
•Yellow: Left stoplamp and turn signal
•Dark Green: Right stoplamp and turn signal
•Dark Blue: Use for electric trailer brakes
•Orange: Trailer accessory
•White (heavy gage): Ground wire
Four-Wire Harness (Trailer Brake Controller)
•Black: Ground
•Red/White Stripe: Fused Battery
•Dark Blue: Trailer Brake Feed
•Light Blue: Fused Stoplamp/CHMSL
4-51 

Service............................................................5-3
Accessories and Modifications..........................5-3
California Proposition 65 Warning.....................5-4
Doing Your Own Service Work.........................5-4
Adding Equipment to the Outside of
Your Vehicle..............................................5-5
Fuel................................................................5-5
Gasoline Octane............................................5-5
Gasoline Specifications....................................5-5
California Fuel...............................................5-6
Additives.......................................................5-6
Fuels in Foreign Countries...............................5-7
Filling the Tank..............................................5-8
Filling a Portable Fuel Container.....................5-10
Checking Things Under the Hood....................5-10
Hood Release..............................................5-11
Engine Compartment Overview.......................5-12
Engine Oil (Gasoline Engine)..........................5-13
Engine Oil Life System (Gasoline Engine)........5-16
Engine Air Cleaner/Filter................................5-17
Automatic Transmission Fluid.........................5-19
Engine Coolant.............................................5-21
Radiator Pressure Cap..................................5-24
Engine Overheating.......................................5-24Cooling System............................................5-26
Engine Fan Noise.........................................5-32
Power Steering Fluid.....................................5-32
Windshield Washer Fluid................................5-34
Brakes........................................................5-35
Battery........................................................5-38
Jump Starting...............................................5-39
All-Wheel Drive..............................................5-43
Rear Axle.......................................................5-44
Front Axle......................................................5-44
Noise Control System.....................................5-45
Tampering with Noise Control System
Prohibited.................................................5-45
Bulb Replacement..........................................5-46
Halogen Bulbs..............................................5-46
Headlamps..................................................5-47
Front Turn Signal, Sidemarker and
Parking Lamps..........................................5-48
Center High-Mounted Stoplamp (CHMSL).........5-49
Taillamps.....................................................5-49
Replacement Bulbs.......................................5-50
Windshield Wiper Blade Replacement..............5-51
Section 5 Service and Appearance Care
5-1 

A. Battery. SeeBattery on page 5-38.
B. Radiator Pressure Cap. SeeRadiator Pressure Cap
on page 5-24.
C. Coolant Recovery Tank. SeeCooling System on
page 5-26.
D. Automatic Transmission Fluid Dipstick. See
“Checking the Fluid Level” underAutomatic
Transmission Fluid on page 5-19.
E. Engine Oil Fill Cap. See “When to Add Engine Oil”
underEngine Oil (Gasoline Engine) on page 5-13.
F. Engine Oil Dipstick. See “Checking Engine Oil” under
Engine Oil (Gasoline Engine) on page 5-13.
G. Engine Air Cleaner/Filter. SeeEngine Air
Cleaner/Filter on page 5-17.
H. Power Steering Fluid Reservoir. SeePower Steering
Fluid on page 5-32.
I. Brake Master Cylinder Reservoir. See “Brake Fluid”
underBrakes on page 5-35.
J. Windshield Washer Fluid Reservoir. See “Adding
Washer Fluid” underWindshield Washer Fluid
on page 5-34.Engine Oil (Gasoline Engine)
If your vehicle has a diesel engine, see “Engine Oil” in
the DURAMAX®Diesel Engine Supplement.
Checking Engine Oil
It is a good idea to check your engine oil every time you
get fuel. In order to get an accurate reading, the oil
must be warm and the vehicle must be on level ground.
The engine oil dipstick handle is a yellow loop. See
Engine Compartment Overview on page 5-12for
the location of the engine oil dipstick.
1. Turn off the engine and give the oil several minutes
to drain back into the oil pan. If you do not do this,
the oil dipstick might not show the actual level.
2. Pull out the dipstick and clean it with a paper towel
or cloth, then push it back in all the way. Remove it
again, keeping the tip down, and check the level.
5-13 

Automatic Transmission Fluid
When to Check and Change Automatic
Transmission Fluid
A good time to check your automatic transmission fluid
level is when the engine oil is changed.
Change the fluid and filter at the intervals listed in
Additional Required Services (Gasoline Engine) on
page 6-6, and be sure to use the transmission fluid listed
inRecommended Fluids and Lubricants (Gasoline
Engine) on page 6-13.
How to Check Automatic Transmission
Fluid
Because this operation can be a little difficult, you may
choose to have this done at the dealership service
department.
If you do it yourself, be sure to follow all the instructions
here, or you could get a false reading on the dipstick.
Notice:Too much or too little  uid can damage
your transmission. Too much can mean that some
of the  uid could come out and fall on hot engine
part or exhaust system parts, starting a  re.
Too little  uid could cause the transmission to
overheat. Be sure to get an accurate reading if you
check your transmission  uid.Wait at least 30 minutes before checking the
transmission fluid level if you have been driving:
•When outside temperatures are above 90°F (32°C).
•At high speed for quite a while.
•In heavy traffic — especially in hot weather.
•While pulling a trailer.
To get the right reading, the fluid should be at normal
operating temperature, which is 180°F to 200°F
(82°C to 93°C).
Get the vehicle warmed up by driving about 15 miles
(24 km) when outside temperatures are above 50°F
(10°C). If it is colder than 50°F (10°C), drive the vehicle
in DRIVE (D) until the engine temperature gage
moves and then remains steady for 10 minutes.
A cold fluid check can be made after the vehicle has
been sitting for eight hours or more with the engine off,
but this is used only as a reference. Let the engine
run at idle for five minutes if outside temperatures are
50°F (10°C) or more. If it is colder than 50°F (10°C), you
may have to idle the engine longer. Should the fluid
level be low during this cold check, you must check the
fluid hot before adding fluid. Checking the fluid hot
will give you a more accurate reading of the fluid level.
5-19 

How to Add Automatic Transmission
Fluid
Refer to the Maintenance Schedule to determine what
kind of transmission fluid to use. SeeRecommended
Fluids and Lubricants (Gasoline Engine) on page 6-13.
Using a funnel, add fluid down the transmission
dipstick tube only after checking the transmission fluid
while it is hot. A cold check is used only as a reference.
If the fluid level is low, add only enough of the proper
fluid to bring the level up to the HOT area for a hot
check. It does not take much fluid, generally less than
one pint (0.5 L). Do not overfill.
Notice:Use of the incorrect automatic transmission
 uid may damage your vehicle, and the damages
may not be covered by your warranty. Always
use the automatic transmission  uid listed in
Recommended Fluids and Lubricants (Gasoline
Engine) on page 6-13.
•After adding fluid, recheck the fluid level as
described under “How to Check Automatic
Transmission Fluid,” earlier in this section.
•When the correct fluid level is obtained, push the
dipstick back in all the way; then flip the handle
down to lock the dipstick in place.
Engine Coolant
The cooling system in your vehicle is filled with
DEX-COOL®engine coolant. This coolant is designed
to remain in your vehicle for five years or 150,000 miles
(240 000 km), whichever occurs first, if you add only
DEX-COOL
®extended life coolant.
The following explains your cooling system and how to
add coolant when it is low. If you have a problem
with engine overheating, seeEngine Overheating on
page 5-24.
A 50/50 mixture of clean, drinkable water and
DEX-COOL
®coolant will:
•Give freezing protection down to−34°F (−37°C).
•Give boiling protection up to 265°F (129°C).
•Protect against rust and corrosion.
•Help keep the proper engine temperature.
•Let the warning lights and gages work as
they should.
Notice:Using coolant other than DEX-COOL
®may
cause premature engine, heater core, radiator
and fuel operated heater (FOH) corrosion. In
addition, the engine coolant may require changing
sooner, at 30,000 miles (50 000 km) or 24 months,
whichever occurs  rst. Any repairs would not
be covered by your warranty. Always use
DEX-COOL
®(silicate-free) coolant in your vehicle.
5-21 

(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 A to Z.
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.Bead:The tire bead contains steel wires wrapped by
steel cords that hold the tire onto the rim.
Bias Ply Tire:A pneumatic tire in which the plies are
laid at alternate angles less than 90 degrees to the
centerline of the tread.
Cold In ation Pressure:The amount of air pressure in
a tire, measured in pounds per square inch (psi) or
kilopascals (kPa) before a tire has built up heat
from driving. SeeIn ation - Tire Pressure on page 5-59.
Curb Weight:This means the weight of a motor
vehicle with standard and optional equipment including
the maximum capacity of fuel, oil and coolant, but
without passengers and cargo.
DOT Markings:A code molded into the sidewall of a
tire signifying that the tire is in compliance with the U.S.
Department of Transportation (DOT) motor vehicle
safety standards. The DOT code includes the Tire
Identification Number (TIN), an alphanumeric designator
which can also identify the tire manufacturer, production
plant, brand and date of production.
GVWR:Gross Vehicle Weight Rating, seeLoading
Your Vehicle on page 4-30.
5-56 

(g)Vehicles with Gross Vehicle Weight Rating (GVWR)
above 10,000 lbs (4 536 kg) only: Inspect shields for
damage or looseness. Adjust or replace as required.
This is a Noise Emission Control Service. Applicable to
vehicles sold in the United States and recommended
for vehicles sold in Canada.
(h)Change automatic transmission  uid and  lter if the
vehicle is mainly driven under one or more of these
conditions:
-In heavy city traffic where the outside temperature
regularly reaches 90°F (32°C) or higher.
-In hilly or mountainous terrain.
-When doing frequent trailer towing.
-Uses such as found in taxi, police, or delivery
service.
(i)Drain,  ush, and re ll cooling system. This service
can be complex; you should have your dealer perform
this service. See Engine Coolant on page 5-21 for
what to use. Inspect hoses. Clean radiator, condenser,
pressure cap, and  ller neck. Pressure test the
cooling system and pressure cap.
(j)A  uid loss in any vehicle system could indicate a
problem. Have the system inspected and repaired and
the  uid level checked. Add  uid if needed.(k)Inspect system. Check all fuel and vapor lines and
hoses for proper hook-up, routing, and condition. Check
that the purge valve works properly, if equipped.
Replace as needed.
(l)If you drive regularly under dusty conditions, inspect
the  lter at each engine oil change.
(m)Check system for interference or binding and for
damaged or missing parts. Replace parts as needed.
Replace any components that have high effort or
excessive wear. Do not lubricate accelerator or cruise
control cables.
(n)Visually inspect belt for fraying, excessive cracks, or
obvious damage. Replace belt if necessary.
Owner Checks and Services
These owner checks and services should be performed
at the intervals specified to help ensure the safety,
dependability, and emission control performance of your
vehicle. Your GM Goodwrench
®dealer can assist you
with these checks and services.
Be sure any necessary repairs are completed at once.
Whenever any fluids or lubricants are added to your
vehicle, make sure they are the proper ones, as shown
inRecommended Fluids and Lubricants (Gasoline
Engine) on page 6-13.
6-9