GMC YUKON DENALI 2008 Owners Manual

If you use a step-bumper hitch, the bumper could be
damaged in sharp turns. Make sure there is ample room
when turning to avoid contact between the trailer and
the bumper.
If you will be pulling a trailer that, when loaded, will
weigh more than 5,000 lbs (2 270 kg) be sure to use a
properly mounted weight-distributing hitch and sway
control of the proper size. This equipment is very
important for proper vehicle loading and good handling
when driving. Always use a sway control if the trailer
will weigh more than these limits. You can ask a
hitch dealer about sway controls.
Hitch Cover
Your vehicle may have a hitch cover. To remove the
hitch cover:
1. Turn the fasteners on the lower tabs 90 degrees
counterclockwise.
2. Lift the lower edge of the cover about 45 degrees.
3. Pull the cover downward to disengage the upper
attachments.To reinstall the hitch cover:
1. Hold the cover at a 45 degree angle to the vehicle
and push the upper tabs in the hitch cover into the
chrome slots in the fascia.
2. Move the bottom of the cover forward until the
lower tabs line up with the lower fascia slots.
3. Snap the hitch cover into place by pushing the
upper corners forward.
4. Turn the fasteners on the lower tabs 90 degrees
clockwise to lock the cover in place.
4-49

Safety Chains
You should always attach chains between your vehicle
and your trailer. Cross the safety chains under the
tongue of the trailer to help prevent the tongue from
contacting the road if it becomes separated from
the hitch. Always leave just enough slack so you can
turn with your rig. Never allow safety chains to drag on
the ground.
Trailer Brakes
If your trailer weighs more than 2,000 lbs (900 kg)
loaded, then it needs its own brakes – and they must be
adequate. Be sure to read and follow the instructions
for the trailer brakes so you’ll be able to install,
adjust and maintain them properly.
Driving with a Trailer
{CAUTION:
If you have a rear-most window open and you
pull a trailer with your vehicle, carbon
monoxide (CO) could come into your vehicle.
You cannot see or smell CO. It can cause
unconsciousness or death. SeeEngine
Exhaust on page 2-38. To maximize your safety
when towing a trailer:
Have your exhaust system inspected for
leaks, and make necessary repairs before
starting on your trip.
Keep the rear-most windows closed.
If exhaust does come into your vehicle
through a window in the rear or another
opening, drive with your front, main
heating or cooling system on and with the
fan on any speed. This will bring fresh,
outside air into your vehicle. Do not use
the climate control setting for maximum air
because it only recirculates the air inside
your vehicle. SeeDual Automatic Climate
Control System on page 3-23.
4-50

Towing a trailer requires a certain amount of experience.
Before setting out for the open road, you’ll want to get
to know your rig. Acquaint yourself with the feel of
handling and braking with the added weight of the trailer.
And always keep in mind that the vehicle you are
driving is now a good deal longer and not nearly as
responsive as your vehicle is by itself.
Before you start, check all trailer hitch parts and
attachments, safety chains, electrical connector, lamps,
tires and mirror adjustment. If the trailer has electric
brakes, start your vehicle and trailer moving and then
apply the trailer brake controller by hand to be sure
the brakes are working. This lets you check your
electrical connection at the same time.
During your trip, check occasionally to be sure that the
load is secure, and that the lamps and any trailer
brakes are still working.Following Distance
Stay at least twice as far behind the vehicle ahead as
you would when driving your vehicle without a trailer.
This can help you avoid situations that require
heavy braking and sudden turns.
Passing
You’ll need more passing distance up ahead when
you’re towing a trailer. And, because you’re a good deal
longer, you’ll need to go much farther beyond the
passed vehicle before you can return to your lane.
Backing Up
Hold the bottom of the steering wheel with one hand.
Then, to move the trailer to the left, just move that hand
to the left. To move the trailer to the right, move your
hand to the right. Always back up slowly and, if possible,
have someone guide you.
4-51

Making Turns
Notice:Making very sharp turns while trailering
could cause the trailer to come in contact with the
vehicle. Your vehicle could be damaged. Avoid
making very sharp turns while trailering.
When you’re turning with a trailer, make wider turns
than normal. Do this so your trailer won’t strike
soft shoulders, curbs, road signs, trees or other objects.
Avoid jerky or sudden maneuvers. Signal well in
advance.
Turn Signals When Towing a Trailer
The arrows on your instrument panel will ash whenever
you signal a turn or lane change. Properly hooked up,
the trailer lamps will also ash, telling other drivers
you’re about to turn, change lanes or stop.
When towing a trailer, the arrows on your instrument
panel will ash for turns even if the bulbs on the trailer
are burned out. Thus, you may think drivers behind
you are seeing your signal when they are not. It’s
important to check occasionally to be sure the trailer
bulbs are still working.
Driving On Grades
Reduce speed and shift to a lower gearbeforeyou start
down a long or steep downgrade. If you don’t shift
down, you might have to use your brakes so much that
they would get hot and no longer work well.
You can tow in DRIVE (D). You may want to shift the
transmission to THIRD (3) or, if necessary, a lower gear
selection if the transmission shifts too often (e.g., under
heavy loads and/or hilly conditions).
You may also want to activate the tow/haul mode if the
transmission shifts too often. See “Tow/Haul Mode”
underTowing a Trailer on page 4-42.
When towing at high altitude on steep uphill grades,
consider the following: Engine coolant at higher altitudes
will boil at a lower temperature than at or near sea
level. 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 5-26.
4-52

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.
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 shift into 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.
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 uid (don’t overll),
engine oil, axle lubricant, belts, cooling system and
brake system. Each of these is covered in this manual,
and the Index will help you nd 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.
4-53

Trailer Wiring Harness
Heavy-Duty Trailer Wiring Package
Your vehicle is equipped with the seven-wire trailer
towing harness. This harness with a seven-pin universal
heavy-duty trailer connector is attached to the rear
bumper beam. It is located next to the integrated
trailer hitch.The seven-wire harness contains the following trailer
circuits:
Yellow: Left Stop/Turn Signal
Dark Green: Right Stop/Turn Signal
Brown: Taillamps
White: Ground
Light Green: Back-up Lamps
Red w/ Black Stripe: Battery Feed*
Dark Blue: Trailer Brake*
*The fuses for these two circuits are installed in the
underhood electrical center, but the circuits are
not connected. They should be installed by your dealer
or a qualied service center.
If you are charging a remote (non-vehicle) battery, press
the tow/haul mode button located at the end of the
shift lever. This will boost the vehicle system voltage and
properly charge the battery. If the trailer is too light for
tow/haul mode, you can turn on the headlamps as
a second way to boost the vehicle system and charge
the battery.
4-54

Electric Brake Control Wiring
Provisions
These wiring provisions are included with your vehicle
as part of the heavy-duty trailer wiring package.
These provisions are for an electric brake controller.
The red/black stripe power feed will not be connected to
the battery until the ring terminal is unstowed and
connected to the underhood electrical center. The
instrument panel contains blunt cut wires near the data
link connector for the trailer brake controller. The
harness contains the following wires:
Dark Blue: Brake Signal to Trailer Connector
Red/Black: Battery
Light Blue/White: Brake Switch
White: Ground
It should be installed by your dealer or a qualied
service center.
Trailer Recommendations
You must subtract your hitch loads from the Cargo
Weight Rating (CWR). CWR is the maximum weight of
the load your vehicle can carry. It doesn’t include
the weight of the people inside, but you can gure about
150 lbs. (68 kg) for each seat. The total cargo load
must not be more than your vehicles CWR.
Weigh your vehicle with your trailer attached, so that
you won’t go over the GVWR or GAWR. If you are using
a weight-distributing hitch, weigh the vehicle without
the spring bars in place.
You’ll get the best performance if you spread out the
weight of your load the right way, and if you choose the
correct hitch and trailer brakes.
For more information seeTowing a Trailer on page 4-42.
4-55

✍NOTES
4-56

Service............................................................5-3
Accessories and Modications..........................5-3
California Proposition 65 Warning.....................5-3
California Perchlorate Materials Requirements.....5-4
Doing Your Own Service Work.........................5-4
Adding Equipment to the Outside
of Your Vehicle...........................................5-4
Fuel................................................................5-5
Gasoline Octane............................................5-5
Gasoline Specications....................................5-5
California Fuel...............................................5-5
Additives.......................................................5-6
Fuels in Foreign Countries...............................5-6
Filling the Tank..............................................5-7
Filling a Portable Fuel Container.......................5-9
Checking Things Under the Hood....................5-10
Hood Release..............................................5-10
Engine Compartment Overview.......................5-12
Engine Oil...................................................5-13
Engine Oil Life System..................................5-16
Engine Air Cleaner/Filter................................5-17
Automatic Transmission Fluid.........................5-20
Engine Coolant.............................................5-23
Coolant Surge Tank Pressure Cap..................5-26
Engine Overheating.......................................5-26
Overheated Engine Protection
Operating Mode........................................5-28Cooling System............................................5-29
Engine Fan Noise.........................................5-34
Power Steering Fluid.....................................5-34
Windshield Washer Fluid................................5-35
Brakes........................................................5-36
Battery........................................................5-39
Jump Starting...............................................5-40
All-Wheel Drive..............................................5-45
Rear Axle.......................................................5-46
Front Axle......................................................5-47
Headlamp Aiming...........................................5-48
Bulb Replacement..........................................5-50
Halogen Bulbs..............................................5-50
Taillamps, Turn Signal, Stoplamps and
Back-up Lamps.........................................5-51
License Plate Lamp......................................5-52
Replacement Bulbs.......................................5-52
Windshield Wiper Blade Replacement..............5-53
Tires..............................................................5-55
Tire Sidewall Labeling...................................5-56
Tire Terminology and Denitions.....................5-58
Ination - Tire Pressure.................................5-60
High-Speed Operation...................................5-62
Tire Pressure Monitor System.........................5-62
Tire Pressure Monitor Operation.....................5-64
Section 5 Service and Appearance Care
5-1

Tire Inspection and Rotation...........................5-67
When It Is Time for New Tires.......................5-69
Buying New Tires.........................................5-70
Different Size Tires and Wheels......................5-72
Uniform Tire Quality Grading..........................5-72
Wheel Alignment and Tire Balance..................5-74
Wheel Replacement......................................5-74
Tire Chains..................................................5-76
If a Tire Goes Flat........................................5-77
Changing a Flat Tire.....................................5-78
Removing the Spare Tire and Tools................5-79
Removing the Flat Tire and Installing the
Spare Tire................................................5-85
Secondary Latch System...............................5-90
Storing a Flat or Spare Tire and Tools............5-94
Spare Tire...................................................5-98
Appearance Care............................................5-98
Interior Cleaning...........................................5-98
Fabric/Carpet..............................................5-100
Leather......................................................5-100
Instrument Panel, Vinyl, and Other Plastic
Surfaces.................................................5-101
Wood Panels..............................................5-101
Speaker Covers..........................................5-101
Care of Safety Belts....................................5-101Weatherstrips.............................................5-101
Washing Your Vehicle..................................5-102
Cleaning Exterior Lamps/Lenses....................5-102
Finish Care................................................5-102
Windshield, Backglass, and Wiper Blades.......5-103
Aluminum Wheels.......................................5-104
Tires.........................................................5-104
Sheet Metal Damage...................................5-105
Finish Damage...........................................5-105
Underbody Maintenance...............................5-105
Chemical Paint Spotting...............................5-105
Vehicle Care/Appearance Materials................5-106
Vehicle Identication.....................................5-107
Vehicle Identication Number (VIN)................5-107
Service Parts Identication Label...................5-107
Electrical System..........................................5-108
Add-On Electrical Equipment.........................5-108
Windshield Wiper Fuses...............................5-108
Power Windows and Other Power Options......5-108
Fuses and Circuit Breakers..........................5-108
Instrument Panel Fuse Block........................5-109
Center Instrument Panel Fuse Block..............5-110
Underhood Fuse Block................................5-111
Capacities and Specications........................5-114
Section 5 Service and Appearance Care
5-2