2008 GMC YUKON XL ECO mode

i(Top Tether Anchor):
Seating positions with top
tether anchors.
For models with a three passenger third row seat, see
the information following for installing a child restraint
with a top tether in the third row, if your vehicle has one.
Never install two top tethers using the same top
tether anchor.
For models with 60/40 second row seating, the rear
right side passenger and center seating positions have
exposed metal anchors located in the crease between
the seatback and the seat cushion.
For models with second row bucket seats, both rear
seating positions have exposed metal anchors located
in the crease between the seatback and the seat
cushion.For models with bucket second row seating, the top
tether anchors are located at the bottom rear of the seat
cushion for each seating position in the second row.
Be sure to use an anchor located on the same side of
the vehicle as the seating position where the child
restraint will be placed. Third Row — Three
Passenger
Second Row Seat — Bucket
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For models with 60/40 second row seating, the top
tether anchors are located at the bottom rear of the seat
cushion for each seating position in the second row.
Be sure to use an anchor located on the same side of
the vehicle as the seating position where the child
restraint will be placed.For vehicles with a two passenger third row seat, there
is one top tether anchor located at the bottom rear
of the seat cushion that can be used for the rear driver
side seating position in the third row. Never install
two top tethers using the same top tether anchor.
For vehicles with a three passenger third row seat, there
is one top tether anchor located at the bottom rear of
the seat cushion that can be used for either the third row
center or driver side seating position. Never install
two top tethers using the same top tether anchor. Second Row Seat — 60/40
Third Row Seat — Two or Three Passenger
1-65

What Makes an Airbag Inate?
In a deployment event, the sensing system sends an
electrical signal triggering a release of gas from
the inator. Gas from the inator lls the airbag causing
the bag to break out of the cover and deploy. The
inator, the airbag, and related hardware are all part of
the airbag module.
Frontal airbag modules are located inside the steering
wheel and instrument panel. For vehicles with
roof-rail airbags, there are airbag modules in the ceiling
of the vehicle, near the side windows that have
occupant seating positions.
How Does an Airbag Restrain?
In moderate to severe frontal or near frontal collisions,
even belted occupants can contact the steering wheel or
the instrument panel. In moderate to severe side
collisions, even belted occupants can contact the inside
of the vehicle.Airbags supplement the protection provided by safety
belts. Frontal airbags distribute the force of the
impact more evenly over the occupant’s upper body,
stopping the occupant more gradually. Roof-rail airbags
distribute the force of the impact more evenly over
the occupant’s upper body.
Rollover capable roof-rail airbags are designed to help
contain the head and chest of occupants in the
outboard seating positions in the rst, second, and third
rows, if equipped with a third row seat. The rollover
capable roof-rail airbags are designed to help reduce the
risk of full or partial ejection in rollover events, although
no system can prevent all such ejections.
But airbags would not help in many types of collisions,
primarily because the occupant’s motion is not
toward those airbags. SeeWhen Should an Airbag
Inflate? on page 1-81for more information.
Airbags should never be regarded as anything more
than a supplement to safety belts.
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Starting the Engine
If your vehicle is a Two-mode Hybrid, see the Two-mode
Hybrid manual for more information.
Move your shift lever to PARK (P) or NEUTRAL (N).
Your engine will not start in any other position – this is a
safety feature. To restart when you are already
moving, use NEUTRAL (N) only.
Notice:Do not try to shift to PARK (P) if your
vehicle is moving. If you do, you could damage the
transmission. Shift to PARK (P) only when your
vehicle is stopped.
Starting Procedure
1. With your foot off the accelerator pedal, turn the
ignition key to START. When the engine starts,
let go of the key. The idle speed will go down as
your engine gets warm. Do not race the engine
immediately after starting it. Operate the engine and
transmission gently to allow the oil to warm up
and lubricate all moving parts.
Your vehicle has a Computer-Controlled Cranking
System. This feature assists in starting the engine
and protects components. If the ignition key is
turned to the START position, and then released
when the engine begins cranking, the engine
will continue cranking for a few seconds or until
the vehicle starts. If the engine does not startand the key is held in START for many seconds,
cranking will be stopped after 15 seconds to prevent
cranking motor damage. To prevent gear damage,
this system also prevents cranking if the engine is
already running. Engine cranking can be stopped by
turning the ignition switch to the ACC/ACCESSORY
or LOCK/OFF position.
Notice:Cranking the engine for long periods of
time, by returning the key to the START position
immediately after cranking has ended, can overheat
and damage the cranking motor, and drain the
battery. Wait at least 15 seconds between each try,
to let the cranking motor cool down.
2. If the engine does not start after 5-10 seconds,
especially in very cold weather (below 0°F or
−18°C), it could be ooded with too much gasoline.
Try pushing the accelerator pedal all the way to
the oor and holding it there as you hold the key in
START for up to a maximum of 15 seconds.
Wait at least 15 seconds between each try, to allow
the cranking motor to cool down. When the
engine starts, let go of the key and accelerator. If
the vehicle starts briey but then stops again, do the
same thing. This clears the extra gasoline from
the engine. Do not race the engine immediately
after starting it. Operate the engine and
transmission gently until the oil warms up and
lubricates all moving parts.
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Active Fuel Management™
Your vehicle’s V8 engine may have Active Fuel
Management™. This system allows the engine to
operate on either all or half of its cylinders, depending
on the driving conditions.
When less power is required, such as cruising at a
constant vehicle speed, the system will operate in the
half cylinder mode, allowing your vehicle to achieve
better fuel economy. When greater power demands are
required, such as accelerating from a stop, passing,
or merging onto a freeway, the system will maintain
full-cylinder operation.
If your vehicle has an Active Fuel Management™
indicator, seeDIC Operation and Displays (With DIC
Buttons) on page 3-56orDIC Operation and Displays
(Without DIC Buttons) on page 3-61for more information
on using this display.
Automatic Transmission Operation
If your vehicle is a Two-mode Hybrid, see the Two-mode
Hybrid manual for more information.
If your vehicle is has an automatic transmission, it has
an electronic shift position indicator within the
instrument panel cluster. This display comes on when
the ignition key is turned to the ON/RUN position.
There are several different positions for the shift lever.
Hydra-Matic
®4-Speed
Automatic Transmission
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MANUAL MODE (M):This position, is available on
vehicles with the Allison Transmission®or Hydra-Matic®
6-Speed transmission. It lets drivers select the range
of gears appropriate for current driving conditions. If your
vehicle has this feature, see Range Select Mode
(Allison Transmission
®or Hydra-Matic®6-Speed
transmission) later in this section.
THIRD (3):This position is also used for normal driving.
It reduces vehicle speed more than DRIVE (D) without
using the brakes. You might choose THIRD (3)
instead of DRIVE (D) when driving on hilly, winding
roads, when towing a trailer, so there is less shifting
between gears and when going down a steep hill.
SECOND (2):This position reduces vehicle speed even
more than THIRD (3) without using your brakes. You can
use SECOND (2) on hills. It can help control your speed
as you go down steep mountain roads, but then you
would also want to use the brakes off and on.
If you manually select SECOND (2) in an automatic
transmission, the transmission will start in second gear.
You can use this feature for reducing the speed of the
rear wheels when you are trying to start your vehicle from
a stop on slippery road surfaces.FIRST (1):For the Hydra-Matic
®4-Speed transmission
this position reduces vehicle speed even more than
SECOND (2) without using the brakes. You can use it
on very steep hills, or in deep snow or mud. If the
shift lever is put in FIRST (1) while the vehicle is moving
forward, the transmission does not shift into rst gear
until the vehicle is going slowly enough.
For an Allison Transmission
®or Hydra-Matic®6-Speed
transmission, this position reduces vehicle speed
without using your brakes. You can use it for
major/severe downgrades and off-road driving where
the vehicle would otherwise accelerate due to steepness
of grade. When you shift to FIRST (1) it provides the
lowest gear appropriate to your current road speed and
continues to downshift as the vehicle slows, eventually
downshifting to FIRST (1) gear.
Notice:Spinning the tires or holding the vehicle in
one place on a hill using only the accelerator
pedal may damage the transmission. The repair will
not be covered by your warranty. If you are stuck,
do not spin the tires. When stopping on a hill,
use the brakes to hold the vehicle in place.
2-35

Low Traction Mode
If your vehicle has the Allison Transmission®,orthe
Hydra-Matic®6-Speed Automatic Transmission, it has a
Low Traction Mode that assist in vehicle acceleration
when road conditions are slippery, such as with ice
or snow. While the vehicle is at a stop, select the second
gear range using the Range Selection system. This
will limit torque to the wheels after it detects wheel slip,
preventing the tires from spinning.
Tow/Haul Mode
Your vehicle has a Tow/Haul mode. The selector button
is located on the end of the column shift lever.You can use this feature to assist when towing or
hauling a heavy load or if there is a need to charge a
battery installed in a trailer. SeeTowing a Trailer
on page 4-49for more information.
When Tow/Haul mode is
selected the Tow/Haul
indicator light will come on.
The Tow/Haul mode works with the Autoride
®feature, if
the vehicle has this, to enhance the ride when
trailering or with a loaded vehicle. SeeAutoride
®on
page 4-49.
2-37

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