towing GMC YUKON DENALI 2008 Owner's Manual

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

If Steam Is Coming From Your Engine
{CAUTION:
Steam from an overheated engine can burn
you badly, even if you just open the hood. Stay
away from the engine if you see or hear steam
coming from it. Turn it off and get everyone
away from the vehicle until it cools down. Wait
until there is no sign of steam or coolant before
you open the hood.
If you keep driving when the vehicles engine is
overheated, the liquids in it can catch re. You
or others could be badly burned. Stop your
engine if it overheats, and get out of the vehicle
until the engine is cool.
SeeOverheated Engine Protection Operating
Mode on page 5-28for information on driving to
a safe place in an emergency.Notice:If your engine catches re because you
keep driving with no coolant, your vehicle can
be badly damaged. The costly repairs would not be
covered by your warranty. SeeOverheated Engine
Protection Operating Mode on page 5-28for
information on driving to a safe place in an
emergency.
If No Steam Is Coming From Your
Engine
The ENGINE OVERHEATED STOP ENGINE or the
ENGINE OVERHEATED IDLE ENGINE message,
along with a low coolant condition, can indicate a
serious problem.
If you get an engine overheat warning, but see or hear
no steam, the problem may not be too serious.
Sometimes the engine can get a little too hot when you:
Climb a long hill on a hot day.
Stop after high-speed driving.
Idle for long periods in traffic.
Tow a trailer. SeeTowing a Trailer on page 4-42.
5-27

If you get the ENGINE OVERHEATED STOP ENGINE
or the ENGINE OVERHEATED IDLE ENGINE message
with no sign of steam, try this for a minute or so:
1. If the vehicle has an air conditioner and it is on,
turn it off.
2. Turn on the heater to the highest temperature and
at the highest fan speed and open the windows as
necessary.
3. In heavy traffic, let the engine idle in NEUTRAL (N)
while stopped. If it is safe to do so, pull off the road,
shift to PARK (P) or NEUTRAL (N) and let the
engine idle.
If you no longer have the overheat warning, you can
drive. Just to be safe, drive slower for about 10 minutes.
If the warning does not come back on, you can drive
normally.
If the warning continues, pull over, stop, and park your
vehicle immediately.
If there is still no sign of steam and your vehicle has an
engine-driven cooling fan, push down the accelerator
until the engine speed is about twice as fast as normal
idle speed for at least ve minutes while parked.
If there is still no sign of steam and your vehicle has an
electric cooling fan, idle the engine for ve minutes
while parked.If you still have the warning, turn off the engine and get
everyone out of the vehicle until it cools down. Also,
see “Overheated Engine Protection Operating Mode”
later in this section.
You might decide not to lift the hood but to get service
help right away.
Overheated Engine Protection
Operating Mode
If an overheated engine condition exists and the
ENGINE POWER IS REDUCED message is displayed,
an overheat protection mode which alternates ring
groups of cylinders helps prevent engine damage. In this
mode, you will notice a loss in power and engine
performance. This operating mode allows your vehicle
to be driven to a safe place in an emergency. Driving
extended miles (km) and/or towing a trailer in the
overheat protection mode should be avoided.
Notice:After driving in the overheated engine
protection operating mode, to avoid engine damage,
allow the engine to cool before attempting any
repair. The engine oil will be severely degraded.
Repair the cause of coolant loss, change the oil and
reset the oil life system. SeeEngine Oil on page 5-13.
5-28

Engine Fan Noise
Your vehicle has electric cooling fans. You might hear
the fans spinning at low speed during most everyday
driving. The fans can turn off if no cooling is required.
Under heavy vehicle loading, trailer towing, and/or
high outside temperatures, or if you are operating the
air conditioning system, the fans can change to high
speed and you might hear an increase in fan noise.
This is normal and indicates that the cooling system is
functioning properly. The fans change to low speed
when additional cooling is no longer required.
Power Steering Fluid
SeeEngine Compartment
Overview on page 5-12for
reservoir location.
When to Check Power Steering Fluid
It is not necessary to regularly check power steering uid
unless you suspect there is a leak in the system or
you hear an unusual noise. A uid loss in this system
could indicate a problem. Have the system inspected
and repaired.
How to Check Power Steering Fluid
To check the power steering uid, do the following:
1. Turn the key off and let the engine compartment
cool down.
2. Wipe the cap and the top of the reservoir clean.
3. Unscrew the cap and wipe the dipstick with a
clean rag.
4. Replace the cap and completely tighten it.
5. Remove the cap again and look at the uid level
on the dipstick.
The level should be at the FULL COLD mark.
If necessary, add only enough uid to bring the
level up to the mark.
5-34

(c)Visually inspect hoses and have them replaced if
they are cracked, swollen, or deteriorated. Inspect all
pipes, fittings, and clamps; replace with genuine parts as
needed. To help ensure proper operation, a pressure test
of the cooling system and pressure cap and cleaning the
outside of the radiator and air conditioning condenser is
recommended at least once a year.
(d)Inspect wiper blades for wear, cracking, or
contamination. Clean the windshield and wiper blades, if
contaminated. Replace wiper blades that are worn or
damaged. See Windshield Wiper Blade Replacement on
page 5-53 and Windshield, Backglass, and Wiper
Blades on page 5-103for more information.
(e)Make sure the safety belt reminder light and safety
belt assemblies are working properly. Look for any
other loose or damaged safety belt system parts. If you
see anything that might keep a safety belt system from
doing its job, have it repaired. Have any torn or frayed
safety belts replaced. Also see Checking the Restraint
Systems on page 1-92.
(f)Lubricate all key lock cylinders, hood latch assembly,
secondary latch, pivots, spring anchor, release pawl,
door hinges, liftgate hinge, liftgate linkage, liftgate handle
pivot points, latch bolt, fuel door hinge, locks, and
folding seat hardware. More frequent lubrication may be
required when exposed to a corrosive environment.
Applying silicone grease on weatherstrips with a clean
cloth will make them last longer, seal better, and not stick
or squeak.(g)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.
(h)Change automatic transmission fluid and filter 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, flush, and refill cooling system. This service
can be complex; you should have your dealer/retailer
perform this service. See Engine Coolant on page 5-23
for what to use. Inspect hoses. Clean radiator,
condenser, pressure cap, and filler neck. Pressure test
the cooling system and pressure cap.
(j)A fluid loss in any vehicle system could indicate a
problem. Have the system inspected and repaired and
the fluid level checked. Add fluid if needed.
(k)If you drive regularly under dusty conditions, inspect
the filter at each engine oil change.
(l)Visually inspect belt for fraying, excessive cracks, or
obvious damage. Replace belt if necessary.
(m)Check vent hose at transfer case for kinks and
proper installation.
6-8

In many instances, mechanical failures may be covered.
However, when other services are utilized, our
Roadside Assistance Representatives will explain any
payment obligations you might incur.
GMC and General Motors of Canada Limited reserve
the right to limit services or reimbursement to an owner
or driver when, in their sole discretion, the claims
become excessive in frequency or type of occurrence.
Calling For Assistance
For prompt and efficient assistance when calling, please
provide the following to the Roadside Assistance
Representative:
Your name, home address, and home telephone
number
Telephone number of your location
Location of the vehicle.
Model, year, color, and license plate number of the
vehicle
Odometer reading, Vehicle Identication Number
(VIN), and delivery date of the vehicle
Description of the problem
Towing and Road Service Exclusions
Specically excluded from Roadside Assistance
coverage are towing or services for vehicles operated
on a non-public roadway or highway, nes, impound
towing caused by a violation of local, Municipal, State,
Provincial, or Federal law, and mounting, dismounting or
changing of snow tires, chains, or other traction devices.
Roadside Assistance is not part of or included in the
coverage provided by the New Vehicle Limited Warranty.
GMC and General Motors of Canada Limited reserve
the right to make any changes or discontinue the
Roadside Assistance program at any time without
notication.
Scheduling Service Appointments
When your vehicle requires warranty service, contact
your dealer/retailer and request an appointment.
By scheduling a service appointment and advising your
service consultant of your transportation needs, your
dealer/retailer can help minimize your inconvenience.
If your vehicle cannot be scheduled into the service
department immediately, keep driving it until it can be
scheduled for service, unless, of course, the problem is
safety-related. If it is, please call your dealership/retailer,
let them know this, and ask for instructions.
If the dealer/retailer requests that you simply drop the
vehicle off for service, you are urged to do so as early
in the work day as possible to allow for the same
day repair.
7-8