2008 HUMMER H3 engine

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
start and 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 ACC/ACCESSORY or LOCK/OFF.
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.
Notice:The engine is designed to work with the
electronics in your vehicle. If you add electrical
parts or accessories, you could change the way the
engine operates. Before adding electrical equipment,
check with your dealer/retailer. If you do not, your
engine might not perform properly. Any resulting
damage would not be covered by your vehicle’s
warranty.
2-21

Engine Coolant Heater
The engine coolant heater, if available, can help in cold
weather conditions at or below 0°F (−18°C) for easier
starting and better fuel economy during engine warm-up.
Plug in the coolant heater at least four hours before
starting your vehicle. An internal thermostat in the
plug-end of the cord may exist which will prevent
engine coolant heater operation at temperatures
above 0° F (−18°C).
To Use the Engine Coolant Heater
1. Turn off the engine.
2. Open the hood and unwrap the electrical cord.
The cord is located in the engine compartment
behind the underhood fuse block on the driver’s
side of the vehicle.
3. Plug it 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/retailer in the area where you will be
parking your vehicle. The dealer/retailer can give you
the best advice for that particular area.
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Automatic Transmission Operation
The automatic transmission has a shift lever on the
console.
It features an electronic shift position indicator within
the instrument cluster. This display must be powered
anytime the shift lever is capable of being moved out of
PARK (P). This means that if your key is turned off,
but not in LOCK, there will be a small current drain on
your battery which could discharge your battery over
a period of time. If you need to leave your key in
the ignition but not in LOCK for an extended period,
it is recommended that you disconnect the battery cable
from the battery to prevent discharging your battery.
There are several different positions for your shift lever.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.
{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).
SeeShifting Into PARK (P) (Automatic
Transmission) on page 2-33. If you are pulling a
trailer, seeTowing a Trailer on page 4-50.
Make sure the shift lever is fully in PARK (P)
before starting the engine. Your vehicle has an
automatic transmission shift lock control system.
You must fully apply your regular brakes rst and
then press the shift lever button before you can
shift from PARK (P) when the ignition key is in ON.
2-23

If you cannot shift out of PARK (P), ease pressure on
the shift lever and push the shift lever all the way
into PARK (P) as you maintain brake application. Then
press the shift lever button and move the shift lever
into another gear. SeeShifting Out of PARK (P)
(Automatic Transmission) on page 2-35
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 4-39
NEUTRAL (N):In this position, your engine does not
connect with the wheels. To restart when you are
already moving, use NEUTRAL (N) only.
{CAUTION:
Shifting into a drive gear while the 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.
2-24

Manual Transmission Operation
This is your shift pattern.
Here is how to operate your manual transmission:
FIRST (1):Press the clutch pedal and shift into
FIRST (1). Then, slowly let up on the clutch pedal as
you slowly press down on the accelerator pedal.
You can shift into FIRST (1) when you are going less
than 20 mph (30 km/h). If you have come to a complete
stop and it is hard to shift into FIRST (1), put the shift
lever in NEUTRAL and let up on the clutch. Then press
the clutch pedal back down and shift into FIRST (1).
SECOND (2):Press the clutch pedal as you let up
on the accelerator pedal and shift into SECOND (2).
Then, slowly let up on the clutch pedal as you press
the accelerator pedal.THIRD, FOURTH AND FIFTH (3, 4 and 5):Shift into
THIRD (3), FOURTH (4) and FIFTH (5) the same
way you do for SECOND (2). Slowly let up on the clutch
pedal as you press the accelerator pedal.
To stop, let up on the accelerator pedal and press the
brake pedal. Just before the vehicle stops, press the
clutch pedal and the brake pedal, and shift to NEUTRAL.
NEUTRAL:Use this position when you start or idle
your engine.
REVERSE (R):To back up, press the clutch pedal.
After the vehicle stops, shift into REVERSE (R).
Slowly let up on the clutch pedal as you press the
accelerator pedal. If it is hard to shift, let the shift lever
return to NEUTRAL and release the clutch pedal.
Then press the clutch again and shift into REVERSE (R).
Do not attempt to shift into the fth gear position prior
to shifting into REVERSE (R). Your transmission has a
lock out feature which prevents a fth gear to reverse
gear shift.
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.
Use REVERSE (R), along with the parking brake,
for parking your vehicle.
2-26

Up-Shift Light
This light will show you
when to shift to the next
higher gear for best
fuel economy.
When this light comes on, you can shift to the next
higher gear if weather, road and traffic conditions permit.
For the best fuel economy, accelerate slowly and shift
when the light comes on.
While you accelerate, it is normal for the light to go
on and off if you quickly change the position of
the accelerator. Ignore the shift light when you
downshift.
If your vehicle has four-wheel drive and has a manual
transmission, disregard the shift light when the transfer
case is in four-wheel low.
For more information, seeUp-Shift Light on page 3-32.
Shift Speeds
{CAUTION:
If you skip a gear when you downshift, you
could lose control of your vehicle. You could
injure yourself or others. Do not shift down
more than one gear at a time when you
downshift.
Full-Time Four-Wheel Drive
Full-Time Four-Wheel Drive sends your engine’s driving
power to all four wheels for extra traction. To get the
most out of Full-Time Four-Wheel Drive, you must
be familiar with its operation.
2-27

Indicator lights in the buttons show which mode you
are in. The indicator lights will come on briey when
you turn on the ignition the mode the vehicle is in
will stay on. If the lights do not come on, you should
take your vehicle to your dealer for service. An indicator
light will ash while shifting the transfer case. It will
remain lit when the shift is complete. If for some reason
the transfer case cannot make a requested shift,
it will return to the last chosen setting.
If the SERV 4WD message on the Driver Information
Center (DIC) stays on, you should take your vehicle to
your dealer for service. See Service 4WD message
underDIC Warnings and Messages on page 3-43.
Shifting between Four-Wheel High
and Four-Wheel-High Lock
With the vehicle traveling less than 45 mph
(72 km/h), press and release the Four-Wheel High
or Four-Wheel-High Lock button. The indicator light
will ash while shifting. It will remain lit when the
shift is complete.
It may be necessary to drive backwards while turning
for a distance of 25 feet (7.5 m) to get the lock
feature to disengage.
Shifting into Four-Wheel Low Lock
Notice:Shifting the transmission into gear before
the indicator light stops ashing could cause
damage to the transfer case. Always wait until the
indicator light stops ashing before putting the
transmission back in gear.
To shift into Four-Wheel-Low Lock, the ignition must be in
ON 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 Low is
to have your vehicle moving 1 to 2 mph (1.6 to 3.2 km/h).
Press and release the Four-Wheel-Low Lock button.
If your vehicle has a manual transmission, the clutch
pedal must be pressed to the oor while you press the
Four-Wheel-Low Lock button, or the shift will not be
completed. You must wait for the Four-Wheel-Low Lock
indicator light to stop ashing and remain lit before
shifting your transmission in gear.
It is normal for your vehicle to have engagement noise
and bump when shifting between Four-Wheel Low
and Four-Wheel High ranges or from NEUTRAL with
the engine running.
If the Four-Wheel-Low Lock button is pressed when
your vehicle is in gear and/or moving too fast, the
Four-Wheel-Low Lock indicator light will ash for
15 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 15 seconds
the transfer case will return to the last chosen setting.
2-29

Shifting Out of Four-Wheel-Low Lock
Notice:Shifting the transmission into gear before
the indicator light stops ashing could cause
damage to the transfer case. Always wait until the
indicator light stops ashing before putting the
transmission back in gear.
To shift out of Four-Wheel-Low Lock, your vehicle must
be stopped or moving less than 3 mph (5 km/h) with the
transmission in NEUTRAL (N) and the ignition in ON. The
preferred method for shifting out of Four-Wheel-Low
Lock is to have your vehicle moving 1 to 2 mph
(1.6 to 3.2 km/h). Press and release the Four-Wheel High
or Four-Wheel-High Lock button. If your vehicle has a
manual transmission, the clutch pedal must be pressed
to the oor while you press the Four-Wheel High or
Four-Wheel-High Lock button, or the shift will not be
completed. You must wait for the Four-Wheel High or
Four-Wheel-High Lock indicator light to stop ashing and
remain lit before shifting your transmission into gear.It is normal for your vehicle to have engagement noise
and bump when shifting between Four-Wheel Low
and Four-Wheel High ranges or from NEUTRAL with
the engine running.
If the Four-Wheel High or Four-Wheel-High Lock button
is pressed when your vehicle is in gear and/or moving
too fast, the Four-Wheel High or Four-Wheel-High Lock
indicator light will ash for 15 seconds but will not
complete the shift unless your vehicle is moving less than
3 mph (5 km/h) and the transmission is in NEUTRAL (N).
Shifting Into NEUTRAL
To shift the transfer case to NEUTRAL, do the following:
1. Set the parking brake.
2. Start the vehicle by turning the ignition to START.
3. Put the transmission in NEUTRAL (N). If your
vehicle has a manual transmission, press and
hold the clutch pedal down while you perform
Steps 5 through 9.
4. Shift the transfer case to Four-Wheel High.
2-30