2007 GMC SIERRA Owner's Manual

Usually, the coolant heater should be plugged in a
minimum of four hours prior to starting your
vehicle. At temperatures above 32°F (0°C), use of
the coolant heater is not required. Your vehicle
may also have an internal thermostat in the
plug end of the cord. This will prevent operation of
the engine coolant heater when the temperature
is at or above 0°F (−18°C) as noted on the cord.
To Use the Engine Coolant Heater
1. Turn off the engine.
2. Open the hood and unwrap the electrical
cord. The cord is located on the driver’s
side of the engine compartment, near
the power steering uid reservoir.
3. Plug the cord into a normal, grounded
110-volt AC outlet.
{CAUTION:
Plugging the cord into an ungrounded
outlet could cause an electrical shock.
Also, the wrong kind of extension cord
could overheat and cause a re. You
could be seriously injured. Plug the cord
into a properly grounded three-prong
110-volt AC outlet. If the cord will not
reach, use a heavy-duty three-prong
extension cord rated for at least 15 amps.
4. Before starting the engine, be sure to unplug
and store the cord as it was before to keep it
away from moving engine parts. If you do
not, it could be damaged.
How long should you keep the coolant heater
plugged in? The answer depends on the outside
temperature, the kind of oil you have, and
some other things. Instead of trying to list
everything here, we ask that you contact your
dealer in the area where you will be parking your
vehicle. The dealer can give you the best
advice for that particular area.
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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.
Your vehicle has an Active Fuel Management™
indicator. For more information on using this
display seeDIC Operation and Displays (With DIC
Buttons) on page 268orDIC Operation and
Displays (Without DIC Buttons) on page 275.
Automatic Transmission Operation
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 RUN position.There are several different positions for the
shift lever.
See “Range Selection Mode” later in this section.
PARK (P):This position locks your rear wheels. It
is the best position to use when you start the engine
because your vehicle cannot move easily.
Hydra-Matic®4-Speed Automatic Transmission
Allison Transmission®or Hydra-Matic®6-Speed
Automatic Transmission
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When parked on a hill, especially when the vehicle
has a heavy load, you might notice an increase in
the effort to shift out of Park. See Torque Lock
(Automatic Transmission) underShifting Into
Park (P) on page 163for more information.
{CAUTION:
It is dangerous to get out of your vehicle
if the shift lever is not fully in PARK (P)
with the parking brake rmly set. Your
vehicle can roll.
Do not leave your vehicle when the engine
is running unless you have to. If you have
left the engine running, the vehicle can
move suddenly. You or others could be
injured. To be sure your vehicle will not
move, even when you are on fairly level
ground, always set your parking brake
and move the shift lever to PARK (P). See
Shifting Into Park (P) on page 163.Ifyou
are pulling a trailer, seeTowing a Trailer
on page 445.
{CAUTION:
If you have Four-Wheel Drive, your vehicle
will be free to roll — even if your shift lever
is in PARK (P) — if your transfer case is in
NEUTRAL. So, be sure the transfer case is
in a drive gear, Two-Wheel Drive High or
Four-Wheel Drive High or Four-Wheel Drive
Low — not in NEUTRAL. SeeShifting Into
Park (P) on page 163.
REVERSE (R):Use this gear to back up.
Notice:Shifting to REVERSE (R) while your
vehicle is moving forward could damage the
transmission. The repairs would not be covered
by your warranty. Shift to REVERSE (R) only
after your vehicle is stopped.
To rock your vehicle back and forth to get out of
snow, ice, or sand without damaging your
transmission, seeIf Your Vehicle is Stuck in Sand,
Mud, Ice, or Snow on page 422.
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NEUTRAL (N):In this position, your engine does
not connect with the wheels. To restart when
you are already moving, use NEUTRAL (N) only.
Also, use NEUTRAL (N) when your vehicle is
being towed.
{CAUTION:
Shifting into a drive gear while your engine
is running at high speed is dangerous.
Unless your foot is rmly on the brake
pedal, your vehicle could move very
rapidly. You could lose control and hit
people or objects. Do not shift into a
drive gear while your engine is running
at high speed.
Notice:Shifting out of PARK (P) or
NEUTRAL (N) with the engine running at high
speed may damage the transmission. The
repairs would not be covered by your warranty.
Be sure the engine is not running at high
speed when shifting your vehicle.DRIVE (D):This position is for normal driving. It
provides the best fuel economy for your vehicle. If
you need more power for passing, and you are:
Going less than about 35 mph (55 km/h),
push your accelerator pedal about
halfway down.
Going about 35 mph (55 km/h) or more, push
the accelerator all the way down.
By doing this, the vehicle shifts down to the
next gear and has more power.
DRIVE (D) can be used when towing a trailer,
carrying a heavy load, driving on steep hills, or for
off-road driving. You might want to shift the
transmission to a lower gear selection if the
transmission shifts too often.
Downshifting the transmission in slippery road
conditions could result in skidding. See Skidding
underLoss of Control on page 389.
Your vehicle has a shift stabilization feature that
adjusts the transmission shifting to the current
driving conditions in order to reduce rapid upshifts
and downshifts.
140

This shift stabilization feature is designed to
determine, before making an upshift, if the engine
is able to maintain vehicle speed by analyzing
things such as vehicle speed, throttle position, and
vehicle load. If the shift stabilization feature
determines that a current vehicle speed cannot be
maintained, the transmission does not upshift
and instead holds the current gear. In some cases,
this could appear to be a delayed shift, however
the transmission is operating normally.
Your vehicle’s transmission uses adaptive shift
controls. Adaptive shift controls continually
compares key shift parameters to pre-programmed
ideal shifts stored in the transmissions computer.
The transmission constantly makes adjustments to
improve vehicle performance according to how the
vehicle is being used, such as with a heavy load or
when temperature changes. During this adaptive
shift control process, shifting might feel different as
the transmission determines the best settings.When temperatures are very cold, the Allison
Transmission®and Hydra-Matic®6-Speed
transmission’s gear shifting could be delayed
providing more stable shifts until the engine warms
up. Shifts could be more noticeable with a cold
transmission. This difference in shifting is normal.
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.
141

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.
142

Range Selection Mode (Allison®or
Hydra-Matic®6-Speed Transmission)
Your vehicle may have a Range Selection Mode.
The Range Selection Mode helps control the
vehicle’s transmission and vehicle speed while
driving down hill or towing a trailer by letting
you select a desired range of gears.To use this feature, do the following:
1. Move the shift lever to the MANUAL
MODE (M).
2. Press the plus/minus buttons, located on the
steering column shift lever, to select the
desired range of gears for your current
driving conditions.
When MANUAL MODE (M) is selected a number
displays next to the M, indicating the current gear.
This number is the highest gear that can be used.
However, your vehicle can automatically shift to
lower gears as it adjusts to driving conditions. This
means that all gears below that number are
available. When FIFTH (5) is selected, FIRST (1)
through FIFTH (5) gears are automatically shifted
by the vehicle, but SIXTH (6) cannot be used until
the plus/minus button located on the steering
column lever is used to change to the gear.
143

Grade Braking is not available when the Range
Selection Mode is active. SeeTow/Haul Mode on
page 144.
While using the Range Selection mode feature,
cruise control and the Tow/Haul mode can
be used.
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.
Low Traction Mode
If your vehicle has the Allison Transmission®,or
the 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
If your vehicle has an automatic transmission, it
has a tow/haul mode. If your vehicle has an Allison
or Hydra-Matic
®6-speed automatic transmission
see “Tow/Haul Mode (Allison or Hydra-Matic®
6-Speed Automatic Transmission®) following.
144