2007 HUMMER H2 engine

To lower the vehicle to the normal ride height,
press the button again. The light in the button will
ash as the suspension lowers. When the light
in the button stops ashing and goes out,
the suspension has reached the normal ride
height.
This feature will lower the vehicle to the normal
height if vehicle speed exceeds 40 mph (64 km/h).
You may also want to use this feature when
ascending, descending or cresting a steep hill as
this can help prevent the rear bumper from
dragging on the base of the hill or prevent the
vehicle from grounding out (high centering) on the
crest of the hill.
Do not use this feature when towing a trailer.Electronically Controlled Air
Suspension System
The electronically controlled air suspension, if
equipped, keeps the rear of your vehicle level as
you load and unload it. The system includes a
compressor, two height sensor and two air springs
supporting the vehicle.
The engine must be running for the system to
level the vehicle after loading or unloading.
The system will suspend transitioning between
the designed ride height and the extended
ride height if any of the doors are open. However,
the system will not suspend operation during
normal leveling and once the doors are closed,
system leveling will continue.
You may hear the compressor running when you
load your vehicle, and periodically as the system
adjusts the vehicle to the standard ride height.
372

If You Do Decide To Pull A Trailer
If you do, here are some important points:
There are many different laws, including speed
limit restrictions, having to do with trailering.
Make sure your rig will be legal, not only
where you live but also where you’ll be driving.
A good source for this information can be
state or provincial police.
Consider using a sway control. See “Hitches”
later in this section.
Don’t tow a trailer at all during the rst
500 miles (800 km) your new vehicle is driven.
Your engine, axle or other parts could be
damaged.
Then, during the rst 500 miles (800 km) that
you tow a trailer, don’t drive over 50 mph
(80 km/h) and don’t make starts at full throttle.
This helps your engine and other parts of
your vehicle wear in at the heavier loads.
You can tow in DRIVE (D). You may want to
shift the transmission to THIRD (3) or, if
necessary, a lower gear selection if the
transmission shifts too often (e.g., under heavy
loads and/or hilly conditions). See “Tow/Haul
Mode” following.
Three important considerations have to do with
weight:
the weight of the trailer
the weight of the trailer tongue
and the weight on your vehicle’s tires
375

Tow/Haul Mode
Tow/haul mode is used when using your vehicle to
pull a large or heavy load or trailer. Tow/haul is
also useful while pulling a load in rolling terrain, in
stop-and-go traffic, or when you need improved
low-speed control, such as when parking.
The purpose of the tow/haul mode is to do the
following:
Reduce the frequency and improve the
predictability of transmission shifts when
pulling a heavy trailer or a large or heavy load.
Provide the same solid shift feel when pulling a
heavy trailer or a large or heavy load as when
the vehicle is unloaded.
Improve control of vehicle speed while requiring
less accelerator pedal activity when pulling a
heavy trailer or a large or heavy load.
Tow/haul mode is most effective when the vehicle
and trailer combined weight is at least 75 percent of
the vehicle’s Gross Combination Weight Rating
(GCWR). See “Weight of the Trailer” later in this
section.Press the button on the
instrument panel to the
right of the steering
wheel to enable
the tow/haul mode.
A light on the instrument
panel will illuminate to
indicate that tow/haul
mode has been
selected.
Press the button again to turn off tow/haul mode.
The indicator light on the instrument panel will
turn off. The vehicle will automatically turn
off tow/haul mode every time it is started.
Driving with tow/haul mode activated without a
heavy load or with no trailer will cause reduced
fuel economy and unpleasant engine and
transmission driving characteristics, but will not
cause damage.
376

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 the following chart to determine how much
your vehicle can weigh, based upon your vehicle
model and options.
Engine Axle Ratio Maximum Trailer Weight **GCWR
6000 V8 (SUV) 4.10 6,700 lbs (3 039 kg) 13,500 lbs (6 123 kg)
6000 V8 (SUT)* 4.10 6,600 lbs (2 994 kg) 13,500 lbs (6 123 kg)
**The Gross Combination Weight Rating (GCWR) in the total allowable weight of the completely loaded vehicle
and trailer including any passengers, cargo, equipment and conversions. The GCWR for your vehicle should not
be exceeded.
*Sport utility truck (SUT) models are neither designed nor intended to tow 5th wheel or gooseneck trailers.
You can ask your dealer for our trailering
information or advice, or you can write us at our
Customer Assistance Offices. SeeCustomer
Assistance Offices on page 540for more
information.
377

Driving On Grades
Reduce speed and shift to a lower gearbefore
you start down a long or steep downgrade. If you
don’t shift down, you might have to use your
brakes so much that they would get hot and no
longer work well.
You can tow in DRIVE (D). You may want to shift
the transmission to THIRD (3) or, if necessary,
a lower gear selection if the transmission shifts too
often (e.g., under heavy loads and/or hilly
conditions).
You may also want to activate the tow/haul mode
if the transmission shifts too often. See “Tow/Haul
Mode” earlier.
When towing at high altitude on steep uphill grades,
consider the following: Engine coolant will boil at a
lower temperature than at normal altitudes. If you
turn your engine off immediately after towing at high
altitude on steep uphill grades, your vehicle may
show signs similar to engine overheating. To avoid
this, let the engine run while parked (preferably on
level ground) with the automatic transmission in
PARK (P) for a few minutes before turning the
engine off. If you do get the overheat warning,
seeEngine Overheating on page 418.
Parking on Hills
{CAUTION:
You really should not park your
vehicle, with a trailer attached, on a hill.
If something goes wrong, your rig could
start to move. People can be injured, and
both your vehicle and the trailer can be
damaged.
But if you ever have to park your rig on a hill,
here’s how to do it:
1. Apply your regular brakes, but don’t shift into
PARK (P) yet.
2. Have someone place chocks under the trailer
wheels.
3. When the wheel chocks are in place, release
the regular brakes until the chocks absorb
the load.
4. Reapply the regular brakes. Then apply your
parking brake and shift into PARK (P).
5. Release the regular brakes.
384

When You Are Ready to Leave After
Parking on a Hill
1. Apply your regular brakes and hold the pedal
down while you:
start your engine,
shift into a gear, and
release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the
chocks.
4. Stop and have someone pick up and store
the chocks.
Maintenance When Trailer Towing
Your vehicle will need service more often when
you’re pulling a trailer. See the Maintenance
Schedule for more on this. Things that are
especially important in trailer operation are
automatic transmission uid (don’t overll),
engine oil, axle lubricant, belts, cooling system
and brake system. Each of these is covered in
this manual, and the Index will help you nd them
quickly. If you’re trailering, it’s a good idea to
review these sections before you start your trip.
Check periodically to see that all hitch nuts
and bolts are tight.
385

Service........................................................ 392
Accessories and Modications................... 392
California Proposition 65 Warning.............. 393
Doing Your Own Service Work.................. 393
Adding Equipment to the Outside of
Your Vehicle.......................................... 394
Fuel............................................................. 394
Gasoline Octane........................................ 394
Gasoline Specications.............................. 394
California Fuel........................................... 395
Additives................................................... 395
Fuels in Foreign Countries........................ 396
Filling the Tank......................................... 397
Filling a Portable Fuel Container............... 399
Checking Things Under the Hood.............. 400
Hood Release........................................... 400
Engine Compartment Overview.................. 402
Engine Oil................................................. 404
Engine Oil Life System.............................. 407
Engine Air Cleaner/Filter............................ 409
Automatic Transmission Fluid.................... 412
Engine Coolant.......................................... 415Coolant Surge Tank Pressure Cap............ 418
Engine Overheating................................... 418
Overheated Engine Protection
Operating Mode..................................... 420
Cooling System......................................... 420
Power Steering Fluid ................................. 425
Windshield Washer Fluid........................... 426
Brakes...................................................... 427
Battery...................................................... 431
Jump Starting............................................ 432
Rear Axle.................................................... 437
Four-Wheel Drive........................................ 438
Front Axle................................................... 440
Bulb Replacement....................................... 441
Halogen Bulbs........................................... 441
Headlamps................................................ 441
Front Turn Signal and Parking Lamps.......... 442
Daytime Running Lamps (DRL)................. 443
Roof Marker Lamps................................... 443
Taillamps, Turn Signal, Stoplamps and
Back-up Lamps...................................... 444
Replacement Bulbs................................... 446
Section 5 Service and Appearance Care
389

California Proposition 65 Warning
Most motor vehicles, including this one, contain
and/or emit chemicals known to the State of
California to cause cancer and birth defects or other
reproductive harm. Engine exhaust, many parts and
systems (including some inside the vehicle), many
uids, and some component wear by-products
contain and/or emit these chemicals.
Doing Your Own Service Work
{CAUTION:
You can be injured and your vehicle could
be damaged if you try to do service work
on a vehicle without knowing enough
about it.
Be sure you have sufficient knowledge,
experience, the proper replacement
parts, and tools before you attempt any
vehicle maintenance task.
CAUTION: (Continued)
CAUTION: (Continued)

Be sure to use the proper nuts, bolts,
and other fasteners. English and
metric fasteners can be easily
confused. If you use the wrong
fasteners, parts can later break or fall
off. You could be hurt.
If you want to do some of your own service work,
you will want to use the proper service manual.
It tells you much more about how to service your
vehicle than this manual can. To order the
proper service manual, seeService Publications
Ordering Information on page 553.
Your vehicle has an airbag system. Before
attempting to do your own service work, see
Servicing Your Airbag-Equipped Vehicle on
page 88.
You should keep a record with all parts receipts
and list the mileage and the date of any service
work you perform. SeeMaintenance Record
on page 532.
393