2003 GMC YUKON engine

Traction Assist System (TAS)
Your vehicle may have a Traction Assist System (TAS)
that limits wheel spin. This is especially useful in
slippery road conditions. The system operates only if it
senses that one or both of the rear wheels are
spinning or beginning to lose traction. When this
happens, the system reduces engine power to limit
wheel spin.
The traction control system is enabled every time your
vehicle is started. The system will activate if it senses
that any of the wheels are spinning or beginning to lose
traction.
You may hear or feel the system working or notice a
lack of accelerator response, but this is normal.
The Traction Assist System may operate on dry roads
under some conditions. When this happens, you
may notice a reduction in acceleration. This is normal
and doesn’t mean there’s a problem with your vehicle.
Examples of these conditions include a hard
acceleration in a turn, an abrupt upshift or downshift of
the transmission or driving on rough roads.If your vehicle is in cruise control when the TAS begins
to limit wheel spin, the cruise control will automatically
disengage. When road conditions allow you to safely
use it again, you may re-engage the cruise control. See
“Cruise Control”underTurn Signal/Multifunction
Lever on page 3-8.
When the traction off light
is on, the TAS is off and
will not limit wheel
spin. Adjust your driving
accordingly.
The traction off light will come on under the following
conditions:
The Traction Assist System is turned off, either by
pressing the TAS on/off button or turning off the
automatic engagement feature of the TAS.
The transmission is in FIRST (1); TAS will not
operate in this gear. This is normal.
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The vehicle is driven on an extremely rough road.
When the vehicle leaves the rough surface, slows
down or stops, the light will go off and TAS will
be on again. This is normal.
A Traction Assist System, Anti-Lock Brake System
or engine-related problem has been detected and
the vehicle needs service.
If the vehicle has been driven with the TAS system
on for long periods of time, or if the vehicle has
gone through many several high speed braking
maneuvers the system may be automatically
disabled. The system will automatically re-enable
after approximately two minutes of not using
the brakes.
SeeTraction Off Light on page 3-45.
The Traction Assist System, as delivered from the
factory, will automatically come on whenever you start
your vehicle. To limit wheel spin, especially in
slippery road conditions, you should always leave the
system on. But you can turn the TAS off if you ever need
to. You should turn the TAS off if your vehicle ever
gets stuck in sand, mud or snow and rocking the vehicle
is required. See“Rocking Your Vehicle”underIf You
Are Stuck: In Sand, Mud, Ice or Snow on page 4-52.To turn the system on or
off, press the TAS on/off
button located on the
instrument panel.
If you used the button to turn the system off, the traction
off light will come on and stay on. You can turn the
system back on at any time by pressing the button
again. The traction off light should go off.
If desired, you can change the TAS automatic
engagement feature so that the system will not come on
automatically when the engine is started. To do so:
1. Park the vehicle with the ignition off and the
transmission in PARK (P).
2. Turn the ignition to RUN; do not start the engine.
3. Apply the brake pedal, shift into NEUTRAL (N),
press the accelerator pedal to theoor and then
press the TAS on/off button and hold it down for at
least six seconds.
4. Release the TAS button and both pedals.
5. Turn off the ignition and wait a few seconds.
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Stabilitrak®and part of the traction control system can
be turned off or back on by pressing the
Stabilitrak
®button. All-wheel drive vehicles must be in
all-wheel drive mode to turn the system on or off.
When the system is turned off, the traction off light will
illuminate, and the STABILITY SYS DISABLED
message will appear on the DIC to warn the driver that
both the stability system and part of the traction
control system are disabled. Your vehicle will still have
brake-traction control when Stabilitrak
®is off, but
will not be able to use the engine speed management
system. See“Traction Control Operation”next for
more information.
When the Stabilitrak
®system has been turned off you
may still hear system noises as a result of the
brake-traction control coming on.
It is recommended to leave the system on for normal
driving conditions, but it may be necessary to turn
the system off if your vehicle is stuck in sand, mud, ice
or snow, and you want to“rock”your vehicle to
attempt to free it. It may also be necessary to turn off
the system when driving in extreme off-road conditions
where high wheel spin is required. SeeIf You Are
Stuck: In Sand, Mud, Ice or Snow on page 4-52.
When the transfer case is in 4 low, the stability system
is automatically disabled, and the STABILITY SYS
DISABLED message will appear on the DIC. In 4 low,
the Stabilitrak
®button only turns the traction control
system on and off.
Traction Control Operation
The traction control system is part of the
Stabilitrak®system. Traction control limits wheel spin by
reducing engine power to the wheels (engine speed
management) and by applying brakes to each individual
wheel (brake-traction control) as necessary.
The traction control system is enabled automatically
when you start your vehicle, and it will activate and
display the TRACTION ACTIVE message in the Driver
Information Center (DIC) if it senses that any of the
wheels are spinning or beginning to lose traction while
driving. If you turn off Stabilitrak
®, only the brake-traction
control portion of traction control will work. The engine
speed management will be disabled. In this state, engine
power is not reduced automatically and the driven wheels
can spin more freely. This can cause the brake-traction
control to activate constantly. For more information on the
traction active message, seeDriver Information Center
(DIC) on page 3-53.
Notice:If the traction off light comes on due to
heavy braking and/or because the traction control
system has been continuously active, do not
allow the wheel(s) of one axle to spin excessively.If
you do, you may be causing damage to your
transfer case.This could lead to costly repairs not
covered by your warranty.
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If the brake-traction control system activates constantly
or if the brakes have heated up due to high speed
braking, the brake-traction control will be automatically
disabled. The system will come back on after the
brakes have cooled. This can take up to two minutes or
longer depending on brake usage.
Notice:Don’t allow the wheel(s) of one axle to spin
excessively when the traction off, ABS and brake
lights are on and the SERVICE STABILITY MESSAGE
is displayed. In this situation, damage to the
transfer case is possible. This could lead to costly
repairs not covered by your warranty. You should
immediately reduce engine power until the lights
and messages are no longer displayed.
The traction control system may activate on dry or
rough roads or under conditions such as heavy
acceleration while turning or abrupt upshifts/downshifts
of the transmission. When this happens you may
notice a reduction in acceleration, or may hear a noise
or vibration. This is normal.
If your vehicle is in cruise control when the system
activates, the STABILITY SYS ACTIVE message will
appear on the Driver Information Center and the cruise
control will automatically disengage. When road
conditions allow you to use cruise again, you may
re-engage the cruise control. See“Cruise Control”under
Turn Signal/Multifunction Lever on page 3-8Stabilitrak®may also turn off automatically if it
determines that a problem exists with the system. If the
problem does not clear itself after restarting the
vehicle, you should see your dealer for service.
Steering
Power Steering
If you lose power steering assist because the engine
stops or the system is not functioning, you can steer but
it will take much more effort.
Steering Tips
Driving on Curves
It’s important to take curves at a reasonable speed.
A lot of the“driver lost control”accidents mentioned on
the news happen on curves. Here’s why:
Experienced driver or beginner, each of us is subject to
the same laws of physics when driving on curves.
The traction of the tires against the road surface makes
it possible for the vehicle to change its path when
you turn the front wheels. If there’s no traction, inertia
will keep the vehicle going in the same direction. If
you’ve ever tried to steer a vehicle on wet ice, you’ll
understand this.
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Of course, traction is reduced when water, snow, ice,
gravel or other material is on the road. For safety, you’ll
want to slow down and adjust your driving to these
conditions. It is important to slow down on slippery
surfaces because stopping distance will be longer and
vehicle control more limited.
While driving on a surface with reduced traction, try
your best to avoid sudden steering, acceleration
or braking (including engine braking by shifting to a
lower gear). Any sudden changes could cause the tires
to slide. You may not realize the surface is slippery
until your vehicle is skidding. Learn to recognize warning
clues—such as enough water, ice or packed snow
on the road to make a“mirrored surface”—and slow
down when you have any doubt.
Remember: Any anti-lock brake system (ABS) helps
avoid only the braking skid.
Off-Road Driving with Your
Four-Wheel-Drive Vehicle
This off-road guide is for vehicles that have four-wheel
drive. Also, seeBraking on page 4-6. If your vehicle
doesn’t have four-wheel drive, you shouldn’t drive
off-road unless you’re on a level, solid surface.Off-road driving can be great fun. But it does have
some denite hazards. The greatest of these is
the terrain itself.
“Off-roading”means you’ve left the great North American
road system behind. Traffic lanes aren’t marked.
Curves aren’t banked. There are no road signs.
Surfaces can be slippery, rough, uphill or downhill. In
short, you’ve gone right back to nature.
Off-road driving involves some new skills. And that’s
why it’s very important that you read this guide.
You’llnd many driving tips and suggestions. These will
help make your off-road driving safer and more
enjoyable.
If you think you will need some more ground clearance
at the front of your vehicle, you can easily remove
the front bumper lower air dam.
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3. Pull the push-pins and
lower air dam assembly
away from the
retainers until the lower
air dam is free.
When you’re back on roads, though, be sure to replace
the air dam.
Notice:Operating your vehicle for extended
periods without the front bumper lower air dam
installed can cause improper air flow to the engine
and may allow things like fog lamps or tow hooks
on the front of your vehicle to be damaged. Always
be sure to replace the front bumper air dam when
you’re finished off-road driving.To reinstall the lower air dam do the following:
1. Line up each push-pin
with its intended
retainer and push the
washer portion of
the push-pin towards
the retainer until it locks
into place.
2. Push theat end of the
push-pin towards the
retainer until it
locks into place,
making sure each is
secure.
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Environmental Concerns
Off-road driving can provide wholesome and satisfying
recreation. However, it also raises environmental
concerns. We recognize these concerns and urge every
off-roader to follow these basic rules for protecting
the environment:
Always use established trails, roads and areas that
have been specially set aside for public off-road
recreational driving; obey all posted regulations.
Avoid any driving practice that could damage
the environment—shrubs,owers, trees,
grasses—or disturb wildlife (this includes
wheel-spinning, breaking down trees or
unnecessary driving through streams or over soft
ground).
Always carry a litter bag—make sure all refuse is
removed from any campsite before leaving.
Take extreme care with openres (where
permitted), camp stoves and lanterns.
Never park your vehicle over dry grass or other
combustible materials that could catchre from
the heat of the vehicle’s exhaust system.
Traveling to Remote Areas
It makes sense to plan your trip, especially when going
to a remote area. Know the terrain and plan your
route. You are much less likely to get bad surprises.
Get accurate maps of trails and terrain. Try to learn of
any blocked or closed roads.
It’s also a good idea to travel with at least one other
vehicle. If something happens to one of them, the other
can help quickly.
Does your vehicle have a winch? If so, be sure to read
the winch instructions. In a remote area, a winch
can be handy if you get stuck. But you’ll want to know
how to use it properly.
Getting Familiar with Off-Road Driving
It’s a good idea to practice in an area that’s safe
and close to home before you go into the wilderness.
Off-road driving does require some new and different
skills. Here’s what we mean.
Tune your senses to different kinds of signals. Your
eyes, for example, need to constantly sweep the terrain
for unexpected obstacles. Your ears need to listen
for unusual tire or engine sounds. With your arms,
hands, feet and body, you’ll need to respond to
vibrations and vehicle bounce.
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Ease up on your speed as you approach the top of
the hill.
Attach aag to the vehicle to make you more
visible to approaching traffic on trails or hills.
Sound the horn as you approach the top of the hill
to let opposing traffic know you’re there.
Use your headlamps even during the day. They
make you more visible to oncoming traffic.
{CAUTION:
Driving to the top (crest) of a hill at full speed
can cause an accident. There could be a
drop-off, embankment, cliff, or even another
vehicle. You could be seriously injured or
killed. As you near the top of a hill, slow down
and stay alert.
Q:What should I do if my vehicle stalls, or is
about to stall, and I can’t make it up the hill?
A:If this happens, there are some things you should
do, and there are some things you must not do.
First, here’s what youshoulddo:
Push the brake pedal to stop the vehicle and keep
it from rolling backwards. Also, apply the parking
brake.
If your engine is still running, shift the transmission
to REVERSE (R), release the parking brake, and
slowly back down the hill in REVERSE (R).
If your engine has stopped running, you’ll need to
restart it. With the brake pedal pressed and the
parking brake still applied, shift the transmission to
PARK (P) and restart the engine. Then, shift to
REVERSE (R), release the parking brake, and
slowly back down the hill as straight as possible in
REVERSE (R).
As you are backing down the hill, put your left hand
on the steering wheel at the 12 o’clock position.
This way, you’ll be able to tell if your wheels
are straight and maneuver as you back down. It’s
best that you back down the hill with your
wheels straight rather than in the left or right
direction. Turning the wheel too far to the left or
right will increase the possibility of a rollover.
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