2010 GMC YUKON DENALI towing

Driving with a Trailer
{WARNING:
When towing a trailer, exhaust gases may collect
at the rear of the vehicle and enter if the liftgate,
trunk/hatch, or rear-most window is open.
Engine exhaust contains carbon monoxide (CO)
which cannot be seen or smelled. It can cause
unconsciousness and even death.
To maximize safety when towing a trailer:
.Have the exhaust system inspected for leaks
and make necessary repairs before starting
a trip.
.Never drive with the liftgate, trunk/hatch,
or rear-most window open.(Continued)
WARNING: (Continued)
.Fully open the air outlets on or under the
instrument panel.
.Adjust the Climate Control system to a setting
that brings in only outside air and set the fan
speed to the highest setting. See Climate
Control System in the Index.
For more information about carbon monoxide, see
Engine Exhaust on page 3‑40.
Towing a trailer requires a certain amount of
experience. The combination you are driving is longer
and not as responsive as the vehicle itself. Get
acquainted with the handling and braking of the rig
before setting out for the open road.
Before starting, check all trailer hitch parts and
attachments, safety chains, electrical connectors,
lamps, tires and mirrors. If the trailer has electric
brakes, start the combination moving and then apply the
trailer brake controller by hand to be sure the
brakes work.
During the trip, check occasionally to be sure that the
load is secure and the lamps and any trailer brakes
still work.
5-56

Following Distance
Stay at least twice as far behind the vehicle ahead as
you would when driving the vehicle without a trailer.
This can help to avoid heavy braking and sudden turns.
Passing
More passing distance is needed when towing a trailer.
The combination will not accelerate as quickly and is
longer so it is necessary to go much farther beyond the
passed vehicle before returning to the lane.
Backing Up
Hold the bottom of the steering wheel with one hand.
Then, to move the trailer to the left, 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.
Making Turns
Notice:Making very sharp turns while trailering
could cause the trailer to come in contact with the
vehicle. The vehicle could be damaged. Avoid
making very sharp turns while trailering.
When turning with a trailer, make wider turns than
normal. Do this so the trailer will not strike soft
shoulders, curbs, road signs, trees or other objects.
Avoid jerky or sudden maneuvers. Signal well in
advance. If the trailer turn signal bulbs burn out, the arrows on the
instrument panel will still flash for turns. It is important to
check occasionally to be sure the trailer bulbs are still
working.
Driving On Grades
Reduce speed and shift to a lower gear
beforestarting
down a long or steep downgrade. If the transmission is
not shifted down, the brakes might get hot and no
longer work well.
Vehicles can tow in D (Drive). Shift the transmission to
a lower gear if the transmission shifts too often under
heavy loads and/or hilly conditions.
The tow/haul mode may be used if the transmission
shifts too often. See Tow/Haul Mode on page 3‑34.
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 the engine
is turned off immediately after towing at high altitude on
steep uphill grades, the 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 P (Park) for a few minutes
before turning the engine off. If the overheat warning
comes on, see Engine Overheating on page 6‑32.
5-57

Parking on Hills
{WARNING:
Parking the vehicle on a hill with the trailer
attached can be dangerous. If something goes
wrong, the rig could start to move. People can be
injured, and both the vehicle and the trailer can be
damaged. When possible, always park the rig on
a flat surface.
If parking the rig on a hill: 1. Press the brake pedal, but do not shift into P (Park) yet. Turn the 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 brake pedal. Then apply the parking brake and shift into P (Park).
5. Release the brake pedal.
Leaving After Parking on a Hill
1. Apply and hold the brake pedal.
2. Start the engine
3. Shift into a gear
4. Release the parking brake
5. Let up on the brake pedal.
6. Drive slowly until the trailer is clear of the chocks.
7. Stop and have someone pick up and store the chocks.
Maintenance When Trailer Towing
The vehicle needs service more often when pulling a
trailer. See this manual's Maintenance Schedule or
Index for more information. Things that are especially
important in trailer operation are automatic transmission
fluid, engine oil, axle lubricant, belts, cooling system
and brake system. It is a good idea to inspect these
before and during the trip.
Check periodically to see that all hitch nuts and bolts
are tight.
5-58

Trailer Wiring Harness
Heavy-Duty Trailer Wiring Harness Package
The vehicle is equipped with the seven-wire trailer
towing harness. This harness with a seven-pin universal
trailer connector is attached to a bracket on the hitch
platform.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: Battery Feed*
.Dark Blue: Trailer Brake*
*The fuses for these two circuits are installed in the
underhood electrical center, but the wires are not
connected. They should be connected by your
dealer/retailer or a qualified service center.
If 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, turn on the headlamps as a second way
to boost the vehicle system and charge the battery.
5-59

Electric Brake Control Wiring
Provisions
These wiring provisions are included with the vehicle as
part of the trailer wiring package. These provisions are
for an electric brake controller. 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/retailer or a
qualified service center.
If the vehicle is equipped with an ITBC, the blunt cuts
exist, but are not connected further in the harness. If an
aftermarket trailer brake controller is installed, the ITBC
must be disconnected. Do not power both ITBC and
aftermarket controllers to control the trailer brakes at the
same time.
Trailer Recommendations
Subtract the hitch loads from the Cargo Weight Rating
(CWR). CWR is the maximum weight of the load the
vehicle can carry. It does not include the weight of the
people inside, but you can figure about 150 lbs. (68 kg)
for each passenger. The total cargo load must not be
more than the vehicles CWR.
Weigh the vehicle with the trailer attached, so the
GVWR or GAWR are not exceeded. If using a
weight-distributing hitch, weigh the vehicle without the
spring bars in place.
The best performance is obtained by correctly
spreading out the weight of the load and choosing the
correct hitch and trailer brakes.
For more information see Towing a Trailer
on
page 5‑42.
5-60

If No Steam Is Coming From The
Engine Compartment
The ENGINE OVERHEATED STOP ENGINE or the
ENGINE OVERHEATED IDLE ENGINE message, along
with a low coolant condition, can indicate a serious
problem.
If an engine overheat warning is displayed but no steam
can be seen or heard, the problem may not be too
serious. Sometimes the engine can get a little too hot
when the vehicle:
.Climbs a long hill on a hot day.
.Stops after high-speed driving.
.Idles for long periods in traffic.
.Tows a trailer. SeeTowing a Trailer on page 5‑42. If the overheat warning is displayed with no sign of
steam:
1. Turn the air conditioning off.
2. Turn the heater on to the highest temperature and to the highest fan speed. Open the windows as
necessary.
3. In heavy traffic, let the engine idle in N (Neutral) while stopped. If it is safe to do so, pull off the
road, shift to P (Park) or N (Neutral) and let the
engine idle.
If the temperature overheat gage is no longer in the
overheat zone or an overheat warning no longer
displays, the vehicle can be driven. Continue to drive
the vehicle slow for about 10 minutes. Keep a safe
vehicle distance from the car in front of you. If the
warning does not come back on, continue to drive
normally.
If the warning continues, pull over, stop, and park the
vehicle right away.
If there is no sign of steam, idle the engine for
three minutes while parked. If the warning is still
displayed, turn off the engine until it cools down.
Also, see “Overheated Engine Protection Operating
Mode” later in this section.
6-34

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 firing
groups of cylinders helps prevent engine damage.
In this mode, you will notice a loss in power and
engine performance. This operating mode allows the
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. See Engine Oil
on
page 6‑15.
Engine Fan Noise
The 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.
6-35

Once a Year
.Starter switch check. SeeOwner Checks and
Services on page 7‑9.
.Parking brake and automatic transmission P (Park)
mechanism check. See Owner Checks and
Services on page 7‑9.
.Automatic transmission shiftlock control system
check. See Owner Checks and Serviceson
page 7‑9.
.Ignition transmission lock check. See Owner
Checks and Services on page 7‑9.
.Hood and liftgate gas strut support service.
Visually inspect gas strut for signs of wear,
corrosion, cracks, loss of lubricant, or other
damage. Check the hold open ability of gas strut.
Replace as necessary with genuine parts from
your dealer/retailer.
.Engine cooling system and pressure cap pressure
check. Radiator and air conditioning condenser
outside cleaning. See Cooling System
on
page 6‑26.
.Exhaust system and nearby heat shields
inspection for loose or damaged components.
.Accelerator pedal check for damage, high effort,
or binding. Replace if needed.
First Engine Oil Change After Every
40 000 km/25,000 Miles
.Fuel system inspection for damage or leaks.
First Engine Oil Change After Every
80 000 km/50,000 Miles
.Engine air cleaner filter replacement. See Engine
Air Cleaner/Filter on page 6‑20.
.Automatic transmission fluid change (severe
service) for vehicles mainly driven in heavy city
traffic in hot weather, in hilly or mountainous
terrain, when frequently towing a trailer, or used for
taxi, police, or delivery service. See Automatic
Transmission Fluid on page 6‑22.
.Transfer case fluid change (severe service) for
vehicles mainly driven when frequently towing a
trailer, or used for taxi, police, or delivery service.
Check vent hose at transfer case for kinks and
proper installation. Check to be sure vent hose is
unobstructed, clear, and free of debris. During any
maintenance, if a power washer is used to clean
mud and dirt from the underbody, care should be
taken to not directly spray the transfer case output
seals. High pressure water can overcome the
seals and contaminate the transfer case fluid.
Contaminated fluid will decrease the life of the
transfer case and should be replaced.
7-6