2007 GMC YUKON Owner's Manual

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. See
Engine Exhaust on page 156. 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.
CAUTION: (Continued)
CAUTION: (Continued)

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 214.
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.
409

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.
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.
410

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 gearbefore
you 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 400.
When towing at high altitude on steep uphill
grades, consider the following: Engine coolant at
or near sea level will boil at a lower temperature
than at higher 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 448.
411

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.
412

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.
413

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.
414

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 400.
415

✍NOTES
416