towing GMC YUKON DENALI 2003 Owner's Manual

Driving with a Trailer
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 can’t see or smell CO.
It can cause
unconsciousness or death. See “Engine
Exhaust” in the Index.
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 comfort control setting for maximum
air because
it only recirculates the air
inside your vehicle. See “Comfort
1 Controls” in the Index. 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 the trailer hitch and platform
(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 a5
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.
4-53

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.
Turn Signals When Towing a Trailer
The arrows on your instrument panel will flash whenever
you signal a turn or lane change. Properly hooked up,
the trailer lamps will also flash, telling other drivers
you’re about
to turn, change lanes or stop.
When towing a trailer, the arrows on your instrument panel will flash for turns even
if the bulbs on the trailer
are burned out. Thus, you may think drivers behind
4-54
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 gear before 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”
under Towing a Trailer
on page 4-47.
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, see Engine Overheating
on
page 5-25.

Parking on Hills
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
2. Have someone place chocks under the trailer
3. When the wheel chocks are in place, release the
PARK
(P) yet.
wheels.
regular brakes until the chocks absorb the load.
4. Reapply the regular brakes. Then apply your
5. Release the regular brakes.
parking brake
and shift into PARK
(P).
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 fluid (don’t overfill),
engine
oil, axle lubricant, belts, 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.
4-55

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 a bracket
on the hitch platform. The Center High-Mounted Stoplamp
(CHMSL) wire is
tied next
to the trailer wiring harness for use with a
trailer.
The seven-wire harness contains the following trailer
circuits:
0 Yellow: Left Stop/Turn Signal
Dark Green: Right Stop/Turn Signal
Brown: Taillamps
White: Ground
Light Green: Back-up Lamps
0 Red: Battery Feed
Dark Blue: Trailer Brake
4-56

Automatic Transmission Fluid
When to Check and Change
A good time to check your automatic transmission fluid
level is when the engine oil is changed.
Change both the fluid and filter every
50,000 miles
(83
000 km) if the vehicle’s GVWR is over 8,600 or 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.
0 In hilly or mountainous terrain.
When doing frequent trailer towing.
Uses such as found in taxi, police or delivery
service.
If your vehicle’s GVWR is not over 8,600 and you do
not use your vehicle under any of these conditions,
change the fluid and filter every
100,000 miles
(1 66 000 km).
How to Check
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 fluid can damage
your transmission. Too much can mean that some of the fluid could come out and fall
on hot engine
part or exhaust system parts, starting a fire.
Too little fluid could cause the transmission to
overheat. Be sure to get an accurate reading if you
check your transmission fluid.
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.
See
Part A: Scheduled Maintenance Services on
page 6-4.
5-20

Adding Coolant
If you need more coolant, add the proper DEX-COOL@
coolant mixture
at the surge tank, but only when the
engine
is cool.
1 “J can be burned if you sb... coolant on hot
engine parts. Coolant contains ethylene glycol, and
it will burn if the engine parts are hot
enough. Don’t spill coolant on a hot engine.
When replacing the pressure cap, make sure it is
hand-tight.
Coolant Surge Tank Pressure Cap
The coolant surge tank pressure cap must be fully
installed on the coolant surge tank. See Engine
Compartment Overview on page
5-12 for more
information on location.
Notice: Your pressure cap is a pressure-type cap
and must be tightly installed to prevent coolant
loss
and possible engine damage from overheating.
See “Capacities and Specifications” for more
information.
Engine Overheating
You will find a coolant temperature gage on your
vehicle’s instrument panel. See Engine Coolant
Temperature Gage
on page 3-36. in addition, yoti ill
find a LOW COOLANT, ENGINE COOLANT HOT,
ENGINE OVERHEATED and a REDUCED ENGINE
POWER message in the DIC on the instrument panel.
See DIC Warnings and Messages on page
3-52.
Overheated Engine Protection
Operating Mode
If an overheated engine condition exists and the
REDUCED ENGINE POWER 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 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. See “Engine Oil” in the Index.
5-25

If No Steam Is Coming From Your
Engine
An overheat warning, along with a low coolant message,
can indicate a serious problem. See
Low Coolant
Level Warning Message under DIC Warnings and
Messages
on page 3-52.
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:
0 Climb a long hill on a hot day.
Stop after high-speed driving.
0 Idle for long periods in traffic.
0 Tow a trailer. See Towing a Trailer on page 4-47.
If you get the overheat warning with no sign of steam, try
this for a minute or so:
1. Turn on your heater to full hot at the highest fan
speed and open the window as necessary.
If you no longer have the overheat warning, you can
drive. Just
to be safe, drive slower for about 10 minutes.
If the warning doesn’t come back on, you can drive
normally.
If the warning continues, pull over, stop, and park your
vehicle right away.
If there’s still no sign of steam, push down the
accelerator until the engine speed is about twice as fast
as normal idle speed for at least three minutes while
you’re 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” listed previously in this section.
You may decide not
to lift the hood but to get service
help right away.
2. If you’re in a traffic jam, shift to NEUTRAL (N);
otherwise, shift to the highest gear while
driving
- DRIVE (D).
5-27

4. With the coolant surge tank pressure cap off, start
the engine and let it run until you can feel the upper
radiator hose getting hot. Watch out for the
engine cooling fan.
By this time, the coolant level inside the coolant
surge tank may be lower. If the level
is lower, add
more of the proper mixture to the coolant surge tank
until the level reaches
FULL COLD mark.
5. Then replace the pressure cap. Be sure the
pressure cap is hand-tight and fully seated.
Engine Fan Noise
Your vehicle has a clutched engine cooling fan. When
the clutch
is engaged, the fan spins faster to provide
more air
tu cool the engine. In most everyday driving
conditions, the fan is spinning slower and the clutch is
not fully engaged. This improves fuel economy and
reduces fan noise. Under heavy vehicle loading, trailer
towing and/or high outside temperatures, the fan
speed increases as the clutch more fully engages.
So
you may hear an increase in fan noise. This is
normal and should not be mistaken as the transmission
slipping or making extra shifts. It is merely the cooling
system functioning properly. The fan will slow down
when additional cooling is not required and the clutch
disengages.
You may also hear this fan noise when you start the
engine.
It will go away as the fan clutch partially
disengages.
5-33

37,500 Miles (62 500 km)
U Check readfront axle fluid level and add fluid as
needed. Check constant velocity joints and axle seals
for leaking.
page 5-56 for proper rotation pattern and additional
information. (See footnote
+.)
U Rotate tires. See Tire inspection and Rotation on
45,000 Miles (75 000 km)
D Check readfront axle fluid level and add fluid as
needed. Check constant velocity joints and axle seals
for leaking.
page 5-56 for proper rotation pattern and additional
information. (See footnote
+.)
U Rotate tires. See Tire Inspection and Rotation on
50,000 Miles (83 000 km)
0 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. if
you do not use your vehicle under any of these
conditions, change the fluid and filter at
100,000 miles
(166
000 km).
52,500 Milles (87 500 km)
U Check readfront axle fluid level and add fluid as
needed. Check constant velocity joints and axle seals
for leaking.
page 5-56 for proper rotation pattern and additional
information. (See footnote
+.)
D Rotate tires. See Tire lnspection and Rotation on
60,000 Miles (100 000 km)
U Check readfront axle fluid level and add fluid as
needed. Check constant velocity joints and axle seals
for leaking.
page 5-56 for proper rotation pattern and additional
information. (See footnote
+.)
Ll Replace fuel filter. An Emission Control Service.
(See footnote
t.)
lJ Inspect Evaporative Control 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.
An Emission Control Service. (See footnote
t.)
U Rotate tires. See Tire lnspection and Rotation on
6-i

100,000 Miles (166 000 km)
0 Inspect spark plug wires. An Emission Control
ii Repiace spark piugs. An Emission Zoniroi Service.
0 Change automatic transmission fluid and filter if
the vehicle is mainly driven under one or more
of these conditions:
Service.
- 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.
Ll If you haven’t used your vehicle under severe service
conditions listed previously and, therefore, haven’t
changed your automatic transmission fluid, change
both the fluid and filter.
150,000 Miles (240 000 km)
0 Drain, flush and refill cooling system (or every
60 months since last service, whichever occurs first). See
Engine Codant on page 5-22 for what to me.
Inspect hoses. Clean radiator, condenser, pressure
cap and neck. Pressure test the cooling system
and pressure cap. An Emission Control Service.
0 Inspect engine accessory drive belt. An Emission
Control Service.
U Inspect Positive Crankcase Ventilation (PCV) valve.
An Emission Control Service.
6-9