automatic transmission GMC YUKON XL 2008 User Guide

Slow ashing means the shift is in progress. It will stay on
when the shift is completed. If for some reason the
transfer case cannot make a requested shift, it will return
to the last chosen setting.
2
m(Two-Wheel Drive High):This setting is used for
driving in most street and highway situations. Your
front axle is not engaged in two-wheel drive. This setting
also provides the best fuel economy.
AUTO (Automatic Four-Wheel Drive):This setting is
ideal for use when road surface traction conditions
are variable. When driving your vehicle in AUTO, the
front axle is engaged, but the vehicle’s power is primarily
sent to the rear wheels. When the vehicle’s software
determines a need for more traction, the system
will transfer more power to the front wheels. Driving in
this mode results in slightly lower fuel economy than
Two-Wheel Drive High.
4
m(Four-Wheel Drive High):Use the four-wheel
high position when you need extra traction, such as on
snowy or icy roads or in most off-road situations.
This setting also engages your front axle to help drive
your vehicle. This is the best setting to use when
plowing snow.
4
n(Four-Wheel Drive Low):This setting also
engages your front axle and delivers extra torque. You
may never need this setting. It sends maximum power to
all four wheels. You might choose Four-Wheel Drive Lowif you are driving off-road in deep sand, deep mud, deep
snow, and while climbing or descending steep hills.
StabiliTrak
®will not engage in this mode. See
StabiliTrak®System on page 4-6for more information.
{CAUTION:
Shifting the transfer case to NEUTRAL can
cause your vehicle to roll even if the
transmission is in PARK (P). You or someone
else could be seriously injured. Be sure to set
the parking brake before placing the transfer
case in NEUTRAL. SeeParking Brake on
page 2-43.
NEUTRAL (N):Shift the vehicle’s transfer case to
NEUTRAL only when towing your vehicle. See
Recreational Vehicle Towing on page 4-45orTowing
Your Vehicle on page 4-45for more information.
If the SERVICE 4 WHEEL DRIVE message stays on,
you should take your vehicle to your dealer for service.
See “SERVICE 4 WHEEL DRIVE message” under
DIC Warnings and Messages on page 3-64.
2-39

Shifting Into Four-Wheel Drive High or
AUTO (Automatic Four-Wheel Drive)
Turn the knob to the Four-Wheel High or AUTO position.
This can be done at any speed, except when shifting
from Four-Wheel Drive Low. The indicator light will ash
while shifting. It will remain on when the shift is
completed.
Shifting Into Two-Wheel Drive High
Turn the knob to the Two-Wheel High position. This can
be done at any speed, except when shifting from
Four-Wheel Drive Low.
See shifting out of Four-Wheel Drive Low later in this
section for more information.
Shifting Into Four-Wheel Drive Low
When Four-Wheel Low is engaged, vehicle speed
should be kept below 45 mph. Extended high-speed
operation in 4L may damage or shorten the life of
the drivetrain.
To shift to the Four-Wheel Drive Low position, the
ignition must be in ON/RUN and the vehicle must be
stopped or moving less than 3 mph (5 km/h) with
the transmission in NEUTRAL (N). The preferred method
for shifting into Four-Wheel Drive Low is to have your
vehicle moving 1 to 2 mph (1.6 to 3.2 km/h).Turn the knob to the Four-Wheel Drive Low position.
You must wait for the Four-Wheel Drive Low indicator
light to stop ashing and remain on before shifting
your transmission in gear.
Notice:Shifting the transmission into gear before
the Four-Wheel Drive Low indicator light has
stopped ashing could damage the transfer case.
To help avoid damaging your vehicle, always
wait for the Four-Wheel Drive Low indicator light to
stop ashing before shifting the transmission
into gear.
The vehicle may have signicant engagement noise and
bump when shifting between Four-Wheel Drive Low
and Four-Wheel Drive High ranges or from NEUTRAL
while the engine is running.
If the knob is turned to the Four-Wheel Drive Low position
when your vehicle is in gear and/or moving, the
Four-Wheel Drive Low indicator light will ash for
30 seconds and not complete the shift unless your
vehicle is moving less than 3 mph (5 km/h) and the
transmission is in NEUTRAL (N). After 30 seconds the
transfer case will shift to Four-Wheel Drive High mode.
2-40

A. Air Outlets. SeeOutlet Adjustment on page 3-33.
B. Turn Signal/Multifunction Lever. SeeTurn
Signal/Multifunction Lever on page 3-7.
C. Instrument Panel Cluster. SeeInstrument Panel
Cluster on page 3-38.
D. Hazard Warning Flasher Button. SeeHazard
Warning Flashers on page 3-6.
E. Shift Lever. SeeAutomatic Transmission Operation
on page 2-31.
F. Tow/Haul Selector Button (If Equipped). See
Tow/Haul Mode on page 2-37.
G. Driver Information Center Controls. SeeDriver
Information Center (DIC) on page 3-55.
H. Audio System. SeeAudio System(s) on page 3-81.
I. Exterior Lamps Control. SeeExterior Lamps on
page 3-16.
J. Dome Lamp Override Button. SeeDome Lamp
Override on page 3-20. Instrument Panel Brightness
Control. SeeInstrument Panel Brightness on
page 3-20. Fog Lamp Button (If Equipped). SeeFog
Lamps on page 3-19.
K. Automatic Transfer Case Control. (If Equipped). See
Four-Wheel Drive on page 2-38.L. Cruise Control Buttons. SeeCruise Control on
page 3-13.
M. Tilt Wheel Lever. SeeTilt Wheel on page 3-6.
N. Horn. SeeHorn on page 3-6.
O. Audio Steering Wheel Controls. SeeAudio Steering
Wheel Controls on page 3-128.
P. Climate Controls. SeeClimate Control System on
page 3-23or Dual Automatic Climate Controls
(If Equipped). SeeDual Automatic Climate Control
System on page 3-26.
Q. Accessory Power Outlets. SeeAccessory Power
Outlet(s) on page 3-22. Cigarette Lighter (If
Equipped). SeeAshtray(s) and Cigarette Lighter on
page 3-23.
R. StabiliTrak
®Button (If Equipped). SeeStabiliTrak®
System on page 4-6. Pedal Adjust Button (If
Equipped). SeeAdjustable Throttle and Brake Pedal
on page 2-29. Rear Park Assist Disable Button (If
Equipped). SeeUltrasonic Rear Parking Assist
(URPA) on page 2-58. Heated Windshield Washer
Fluid Button (If Equipped). SeeWindshield Washer on
page 3-11. Power Running Boards Disable Button (If
Equipped). SeePower Running Boards on page 2-18.
S. Glove Box. SeeGlove Box on page 2-71.
3-5

;(Parking Lamps):Turn the control to this position
to turn on the parking lamps together with the
following:
Instrument Panel Lights
Taillamps
License Plate Lamps
2(Headlamps):Turn the control to this position to
turn on the headlamps together with the following lamps
listed below.
Parking Lamps
Instrument Panel Lights
Taillamps
License Plate Lamps
When the headlamps are turned on while the vehicle is
on, the headlamps turn off automatically 10 minutes
after the ignition is turned off. When the headlamps are
turned on while the vehicle is off, the headlamps will
stay on for 10 minutes before automatically turning off to
prevent the battery from being drained.
Headlamps on Reminder
A reminder chime will sound when the headlamps or
parking lamps are manually turned on and your ignition
is off and a door is open. To disable the chime, turn
the light off.
Daytime Running Lamps (DRL)
Daytime Running Lamps (DRL) can make it easier for
others to see the front of your vehicle during the
day. DRL can be helpful in many different driving
conditions, but they can be especially helpful in the short
periods after dawn and before sunset. Fully functional
daytime running lamps are required on all vehicles
rst sold in Canada.
The DRL system will come on when the following
conditions are met:
The ignition is on.
The exterior lamps control is in AUTO.
The transmission is not in PARK (P).
The light sensor determines it is daytime.
When the DRL are on, only the DRL lamps will be on.
The taillamps, sidemarker, and other lamps will not
be on. The instrument panel will not be lit up either.
3-17

When it begins to get dark, the automatic headlamp
system will switch from DRL to the headlamps.
To turn off the DRL lamps, turn the exterior lamps
control to the OFF position and then release. For
vehicles rst sold in Canada, the transmission must be
in the PARK (P) position, before the DRL lamps can
be turned off.
Automatic Headlamp System
When it is dark enough outside, the automatic headlamp
system will turn on the headlamps at the normal
brightness, along with the taillamps, sidemarker, parking
lamps, and the instrument panel lights. The radio
lights will also be dim.
To turn off the automatic headlamp system, turn the
exterior lamps switch to the off position and then release
it. For vehicles rst sold in Canada, the transmission
must be in the PARK (P) position, before the automatic
headlamp system can be turned off.
The vehicle has a light sensor located on the top of the
instrument panel in the defroster grille that regulates
when the automatic headlamps turn on. Be sure it is not
covered, or the headlamps will come on whenever
the ignition is on.
The system may also turn on the headlamps when
driving through a parking garage, heavy overcast
weather, or a tunnel. This is normal.There is a delay in the transition between the daytime
and nighttime operation of the Daytime Running
Lamps (DRL) and the automatic headlamp systems so
that driving under bridges or bright overhead street
lights does not affect the system. The DRL and
automatic headlamp system will only be affected when
the light sensor detects a change in lighting lasting
longer than the delay.
If the vehicle is started in a dark garage, the automatic
headlamp system will come on immediately. Once
the vehicle leaves the garage, it takes approximately
one minute for the automatic headlamp system to
change to DRL if it is bright enough outside. During that
delay, the instrument panel cluster may not be as
bright as usual. Make sure the instrument panel
brightness control is in the full bright position. See
Instrument Panel Brightness on page 3-20.
To idle the vehicle with the automatic headlamp system
off, turn the control to the off position.
The headlamps will also stay on after you exit the
vehicle. This feature can be programmed using the
Driver Information Center (DIC). SeeDIC Vehicle
Customization (With DIC Buttons) on page 3-72.
The regular headlamp system can be turned on when
needed.
3-18

Transmission Temperature
Press the trip/fuel button until TRANS TEMP displays.
This display shows the temperature of the automatic
transmission uid in either degrees Fahrenheit (°F) or
degrees Celsius (°C).
Instantaneous Economy and Active Fuel
Management™ Indicator
If your vehicle has this display, press the trip/fuel button
until INST ECONOMY V8 MODE displays. This
display shows the current fuel economy at a particular
moment and will change frequently as driving conditions
change. This display shows the instantaneous fuel
economy in miles per gallon (mpg) or liters per
100 kilometers (L/100 km). Unlike average economy,
this screen cannot be reset.
An Active Fuel Management™ indicator will display on
the right side of the DIC, while INST ECONOMY
displays on the left side. Active Fuel Management™
allows the engine to operate on either four or eight
cylinders, depending on your driving demands. When
Active Fuel Management™ is active, V4 MODE will
display on the DIC. When Active Fuel Management™ is
inactive, V8 MODE will display. SeeActive Fuel
Management™ on page 2-31for more information.
Blank Display
This display shows no information.
Vehicle Information Menu Items
T
(Vehicle Information):Press this button to scroll
through the following menu items:
Oil Life
Press the vehicle information button until OIL LIFE
REMAINING displays. This display shows an estimate
of the oil’s remaining useful life. If you see 99% OIL LIFE
REMAINING on the display, that means 99% of the
current oil life remains. The engine oil life system
will alert you to change the oil on a schedule consistent
with your driving conditions.
When the remaining oil life is low, the CHANGE
ENGINE OIL SOON message will appear on the display.
See “CHANGE ENGINE OIL SOON” underDIC
Warnings and Messages on page 3-64. You should
change the oil as soon as you can. SeeEngine Oil on
page 5-15. In addition to the engine oil life system
monitoring the oil life, additional maintenance is
recommended in the Maintenance Schedule in this
manual. SeeScheduled Maintenance on page 6-4for
more information.
3-59

TRANSMISSION HOT IDLE ENGINE
Notice:If you drive your vehicle while the
transmission uid is overheating and the
transmission temperature warning is displayed on
the instrument panel cluster and/or DIC, you
can damage the transmission. This could lead to
costly repairs that would not be covered by
your warranty. Do not drive your vehicle with
overheated transmission uid or while the
transmission temperature warning is displayed.
This message displays along with a continuous chime if
the transmission uid in the vehicle gets hot. Driving
with the transmission uid temperature high can cause
damage to the vehicle. Stop the vehicle and let it
idle to allow the transmission to cool. This message
clears and the chime stops when the uid temperature
reaches a safe level.
TURN SIGNAL ON
This message displays and a chime sounds if a turn
signal is left on for 3/4 of a mile (1.2 km). Move the turn
signal/multifunction lever to the off position.
WASHER FLUID LOW ADD FLUID
This message displays when the windshield washer
uid is low. Fill the windshield washer uid reservoir as
soon as possible. SeeEngine Compartment Overview
on page 5-14for the location of the windshield
washer uid reservoir. Also, seeWindshield Washer
Fluid on page 5-40for more information.
DIC Vehicle Customization
(With DIC Buttons)
Your vehicle may have customization capabilities that
allow you to program certain features to one preferred
setting. Customization features can only be programmed
to one setting on the vehicle and cannot be programmed
to a preferred setting for two different drivers.
All of the customization options may not be available on
your vehicle. Only the options available will be
displayed on the DIC.
The default settings for the customization features were
set when your vehicle left the factory, but may have
been changed from their default state since then.
The customization preferences are automatically
recalled.
To change customization preferences, use the following
procedure.
3-72

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. It will activate and the
StabiliTrak
®light will ash if it senses that any of the
wheels are spinning or beginning to lose traction while
driving. If you turn off traction control, only the
brake-traction control portion of traction control will
work. The engine speed management will be disabled.
In this mode, engine power is not reduced automatically
and the driven wheels can spin more freely. This can
cause the brake-traction control to activate constantly.
Notice:If you allow the wheel(s) of one axle to spin
excessively while the StabiliTrak
®, ABS and brake
warning lights and the SERVICE STABILITRAK
message are displayed, you could damage the
transfer case. The repairs would not be covered by
your warranty. Reduce engine power and do not
spin the wheel(s) excessively while these lights and
this message are 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 StabiliTrak
®light will ash and the cruise
control will automatically disengage. When road
conditions allow you to use cruise again, you may
re-engage the cruise control. SeeCruise Control on
page 3-13.
StabiliTrak
®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/retailer for service.
4-8

Dolly Towing
Two-Wheel-Drive Vehicles
Notice:If you tow a two-wheel-drive vehicle with
the rear wheels on the ground, the transmission
could be damaged. The repairs would not be
covered by your warranty. Never tow your vehicle
with the rear wheels on the ground.
Two-wheel-drive vehicles should not be towed with the
rear wheels on the ground. Two-wheel-drive
transmissions have no provisions for internal lubrication
while being towed.
Two-wheel-drive vehicles can be towed on a dolly with
the front wheels on the ground provided that the
wheels are straight.
Four-Wheel-Drive Vehicles
Four-wheel-drive vehicles are not designed to be dolly
towed. If you need to tow your vehicle, see “Dinghy
Towing” earlier in this section.
Level Control
Automatic Level Control
The automatic level control rear suspension is available
on two-wheel drive and four-wheel drive light-duty
vehicles and comes as a part of the Autoride
®
suspension, if equipped.
This type of level control is fully automatic and will
provide a better leveled riding position as well as better
handling under a variety of passenger and loading
conditions. An air compressor connected to the rear
shocks will raise or lower the rear of the vehicle
to maintain proper vehicle height. The system is
activated when the ignition key is turned to RUN and
will automatically adjust vehicle height thereafter.
The system may exhaust (lower vehicle height) for up to
ten minutes after the ignition key has been turned off.
You may hear the air compressor operating when
the height is being adjusted.
If a weight-distributing hitch is being used, it is
recommended to allow the shocks to inate, thereby
leveling the vehicle prior to adjusting the hitch.
4-48

Your vehicle is equipped with a button at the end of the
shift lever which, when pressed, enables tow/haul.
Your vehicle may be equipped with Autoride
®which
further improves your vehicle’s ride while towing.
SeeAutoride
®on page 4-49for more information. When
the button is pressed, a light on the instrument panel
will illuminate to indicate that Tow/Haul has been
selected. Tow/Haul may be turned off by pressing the
button again, at which time the indicator light on
the instrument panel will turn off. The vehicle will
automatically turn off Tow/Haul every time it is started.
Tow/Haul is designed to be most effective when the
vehicle and trailer combined weight is at least 75 percent
of the vehicle’s Gross Combined Weight Rating
(GCWR). See Weight of the Trailer later in this section.
Tow/Haul is most useful under the following driving
conditions:
When pulling a heavy trailer or a large or heavy
load through rolling terrain.
When pulling a heavy trailer or a large or heavy
load in stop and go traffic.
When pulling a heavy trailer or a large or heavy
load in busy parking lots where improved low
speed control of the vehicle is desired.Operating the vehicle in tow/haul when lightly loaded or
with no trailer at all will not cause damage. However,
there is no benet to the selection of Tow/Haul when the
vehicle is unloaded. Such a selection when unloaded
may result in unpleasant engine and transmission driving
characteristics and reduced fuel economy. Tow/Haul
is recommended only when pulling a heavy trailer or a
large or heavy load.
Weight of the Trailer
How heavy can a trailer safely be?
It depends on how you plan to use your rig. For
example, speed, altitude, road grades, outside
temperature and how much your vehicle is used to pull
a trailer are all important. It can also depend on any
special equipment that you have on your vehicle,
and the amount of tongue weight the vehicle can carry.
See “Weight of the Trailer Tongue” later in this
section for more information.
Maximum trailer weight is calculated assuming only the
driver is in the tow vehicle and it has all the required
trailering equipment. The weight of additional optional
equipment, passengers and cargo in the tow vehicle
must be subtracted from the maximum trailer weight.
Use one of the following charts to determine how much
your vehicle can weigh, based upon your vehicle
model and options.
4-52