
Maintenance When Trailer Towing
The vehicle needs service more often when pulling a
trailer. See this manual’s Maintenance Schedule or Index
for more information. Things that are especially important
in trailer operation are automatic transmission uid,
engine oil, axle lubricant, belts, cooling system and brake
system. It is a good idea to inspect these before and
during the trip.
Check periodically to see that all hitch nuts and bolts
are tight.
Trailer Wiring Harness
Heavy-Duty Trailer Wiring Harness
Package
The vehicle is equipped with the seven-wire trailer towing
harness. This harness with a seven-pin universal trailer
connector is attached to a bracket on the hitch platform.The seven-wire harness contains the following trailer
circuits:
Yellow: Left Stop/Turn Signal
Dark Green: Right Stop/Turn Signal
Brown: Taillamps
White: Ground
Light Green: Back-up Lamps
Red/Black: Battery Feed*
Dark Blue: Trailer Brake*
*There is a location in the Underhood Fuse Block for
these circuits, but they are not connected. They should
be connected, and proper fuses installed, by your
dealer/retailer or a quali ed service center.
If charging a remote (non-vehicle) battery, press the
Tow/Haul mode button located at the end of the
shift lever. This will boost the vehicle system voltage
and properly charge the battery.
4-67

Electric Brake Control Wiring
Provisions
These wiring provisions are included with the vehicle
as part of the trailer wiring package. These provisions
are for an electric brake controller. The instrument panel
contains blunt cut wires near the data link connector
for the trailer brake controller. The harness contains
the following wires:
Dark Blue: Brake Signal to Trailer Connector
Red/Black: Battery
Light Blue/White: Brake Switch
White: Ground
It should be installed by your dealer/retailer or a
quali ed service center.
Trailer Recommendations
Subtract the hitch loads from the Cargo Weight Rating
(CWR). CWR is the maximum weight of the load
the vehicle can carry. It does not include the weight of
the people inside, but you can gure about 150 lbs.
(68 kg) for each passenger. The total cargo load must
not be more than the vehicles CWR.
Weigh the vehicle with the trailer attached, so the GVWR
or GAWR are not exceeded. If using a weight-distributing
hitch, weigh the vehicle without the spring bars in place.
The best performance is obtained by correctly spreading
out the weight of the load and choosing the correct
hitch and trailer brakes.
For more information seeTowing a Trailer on page 4-55.
4-68

If Steam Is Coming From the Engine
{CAUTION:
Steam from an overheated engine can burn you
badly, even if you just open the hood. Stay away
from the engine if you see or hear steam coming
from it. Turn it off and get everyone away from the
vehicle until it cools down. Wait until there is no sign
of steam or coolant before you open the hood.
If you keep driving when the vehicles engine is
overheated, the liquids in it can catch re. You or
others could be badly burned. Stop the engine if it
overheats, and get out of the vehicle until the
engine is cool.
SeeOverheated Engine Protection Operating Mode
on page 5-35for information on driving to a safe
place in an emergency.Notice:If the engine catches re while driving with
no coolant, the vehicle can be badly damaged.
The costly repairs would not be covered by
the vehicle warranty. SeeOverheated Engine
Protection Operating Mode on page 5-35for
information on driving to a safe place in an
emergency.
If No Steam Is Coming From the
Engine
The ENGINE OVERHEATED IDLE ENGINE message,
along with a low coolant condition, can indicate a
serious problem.
If you get an engine overheat warning, but see or hear
no steam, the problem may not be too serious.
Sometimes the engine can get a little too hot when you:
Climb a long hill on a hot day.
Stop after high-speed driving.
Idle for long periods in traffic.
Tow a trailer. SeeTowing a Trailer on page 4-55.
5-34

If you get the ENGINE COOLANT HOT message with
no sign of steam, try this for a minute or so:
1. Turn on the heater to full hot at the highest fan
speed and open the windows as necessary.
2. If you are in a traffic jam, shift to N (Neutral);
otherwise, shift to the highest gear while
driving—D(Drive).
If you no longer have the overheat warning, you can
drive. Just to be safe, drive slower for about 10 minutes.
If the warning does not come back on, you can drive
normally.
If the warning continues and you have not stopped, pull
over, stop, and park the vehicle right away.
If there is still no sign of steam, push down the
accelerator until the engine speed is about twice as fast
as normal idle speed for at least three minutes while
you are parked. If you still have the warning, turn off the
engine and get everyone out of the vehicle until it
cools down. Also, see “Overheated Engine Protection
Operating Mode” later in this section.
You may decide not to lift the hood but to get service
help right away.Overheated Engine Protection
Operating Mode
If an overheated engine condition exists and the
ENGINE POWER IS REDUCED message is displayed,
an overheat protection mode which alternates ring
groups of cylinders helps prevent engine damage. In this
mode, you will notice a loss in power and engine
performance. This operating mode allows the vehicle to
be driven to a safe place in an emergency. Driving
extended miles (km) and/or towing a trailer in the
overheat protection mode should be avoided.
Notice:After driving in the overheated engine
protection operating mode, to avoid engine damage,
allow the engine to cool before attempting any
repair. The engine oil will be severely degraded.
Repair the cause of coolant loss, change the oil and
reset the oil life system. SeeEngine Oil on
page 5-15.
5-35

(d)Inspect wiper blades for wear, cracking, or
contamination. Clean the windshield and wiper blades, if
contaminated. Replace wiper blades that are worn or
damaged. See Windshield Wiper Blade Replacement on
page 5-56 and Windshield, Backglass, and Wiper Blades
on page 5-107 for more information.
(e)Make sure the safety belt reminder light and safety
belt assemblies are working properly. Look for any
other loose or damaged safety belt system parts. If you
see anything that might keep a safety belt system
from doing its job, have it repaired. Have any torn or
frayed safety belts replaced. Also see Checking
the Restraint Systems on page 1-80.
(f)Lubricate all key lock cylinders, hood latch assembly,
secondary latch, pivots, spring anchor, release pawl,
rear compartment hinges, outer liftgate handle pivot
points, rear door detent link, roller mechanism, liftgate
handle pivot points, latch bolt, fuel door hinge, cargo door
hinge, locks, and folding seat hardware. More frequent
lubrication may be required when exposed to a corrosive
environment. Applying silicone grease on weatherstrips
with a clean cloth will make them last longer, seal better,
and not stick or squeak.Spare tire carrier hinge and latch: Inspect for leaks and
lubricate if required. Remove the setscrew at the hinge
casting and add lubricant, moving the hinge back and
forth periodically, until lubricant can be seen coming
from the setscrew opening. Install setscrew and tighten
to7ftlb(9Y). SeeRecommended Fluids and
Lubricants on page 6-13 for what lubricant to use.
(g)Check vent hose at transfer case for kinks and
proper installation. Check to be sure vent hose is
unobstructed, clear, and free of debris. During any
maintenance, if a power washer is used to clean mud
and dirt from the underbody, care should be taken to
not directly spray the transfer case output seals.
High pressure water can overcome the seals and
contaminate the transfer case fluid. Contaminated fluid
will decrease the life of the transfer case and should
be replaced.
(h)Change automatic transmission fluid and filter if the
vehicle is mainly driven under one or more of these
conditions:
In heavy city traffic where the outside temperature
regularly reaches 90°F (32°C) or higher.
In hilly or mountainous terrain.
When doing frequent trailer towing.
Uses such as found in taxi, police, or delivery
service.
6-8

(i)Drain, flush, and refill cooling system. This service can
be complex; you should have your dealer/retailer perform
this service. See Engine Coolant on page 5-31 for what to
use. Inspect hoses. Clean radiator, condenser, pressure
cap, and filler neck. Pressure test the cooling system and
pressure cap.
(j)A fluid loss in any vehicle system could indicate a
problem. Have the system inspected and repaired and
the fluid level checked. Add fluid if needed.
(k)Visually inspect belt for fraying, excessive cracks, or
obvious damage. Replace belt if necessary.
(l)Severe Service: Change transfer case fluid if the
vehicle is mainly used for trailer towing or driven in city
traffic, wet environment, or high ambient temperatures.
Owner Checks and Services
These owner checks and services should be performed
at the intervals speci ed to help ensure vehicle safety,
dependability, and emission control performance. Your
dealer/retailer can assist with these checks and services.
Be sure any necessary repairs are completed at once.
Whenever any uids or lubricants are added to the
vehicle, make sure they are the proper ones, as shown
inRecommended Fluids and Lubricants on page 6-13.
At Each Fuel Fill
It is important to perform these underhood checks at
each fuel fill.
Engine Oil Level Check
Notice:It is important to check the engine oil
regularly and keep it at the proper level. Failure to
keep the engine oil at the proper level can cause
damage to the engine not covered by the vehicle
warranty.
Check the engine oil level and add the proper oil if
necessary. SeeEngine Oil on page 5-15.
Engine Coolant Level Check
Check the engine coolant level and add DEX-COOL®
coolant mixture if necessary. SeeEngine Coolant
on page 5-31.
Windshield Washer Fluid Level Check
Check the windshield washer uid level in the windshield
washer uid reservoir and add the proper uid if
necessary.
6-9

HUMMER Technician Roadside Service
(U.S. only)
HUMMER’s exceptional Roadside Service is more
than an auto club or towing service. It provides every
HUMMER owner in the United States with the advantage
of contacting a HUMMER advisor and, where available, a
HUMMER trained dealer technician who can provide
on-site service.
A dealer technician will travel to your location within a
30 mile radius of a participating HUMMER dealership.
If beyond this radius, we will arrange to have your
vehicle towed to the nearest HUMMER dealership.
Each technician travels with a specially equipped service
vehicle complete with the necessary HUMMER parts
and tools required to handle most roadside repairs.
Services Not Included in Roadside
Assistance
Impound towing caused by violation of any laws.
Legal nes.
Mounting, dismounting or changing of snow tires,
chains, or other traction devices.
Towing or services for vehicles driven on a
non-public road or highway.
Services Speci c to Canadian
Purchased Vehicles
Fuel delivery:Reimbursement is approximately
$5 Canadian. Diesel fuel delivery may be restricted.
Propane and other fuels are not provided through
this service.
Lock-Out Service:Vehicle registration is required.
Trip Routing Service:Limit of six requests
per year.
Trip Interruption Bene ts and Assistance:
Pre-authorization, original detailed receipts, and a
copy of the repair orders are required. Once
authorization has been received, the Roadside
Assistance advisor will help you make arrangements
and explain how to receive payment.
Alternative Service:If assistance cannot be
provided right away, the Roadside Assistance
advisor may give you permission to get local
emergency road service. You will receive payment,
up to $100, after sending the original receipt to
Roadside Assistance. Mechanical failures may be
covered, however any cost for parts and labor for
repairs not covered by the warranty are the owner
responsibility.
7-9

If a Crash Occurs
Here is what to do if you are involved in a crash.
Try to relax and then check to make sure you are all
right. If you are uninjured, make sure that no one else
in your vehicle, or the other vehicle, is injured.
If there has been an injury, call emergency services
for help. Do not leave the scene of a crash until all
matters have been taken care of. Move your vehicle
only if its position puts you in danger or you are
instructed to move it by a police officer.
Give only the necessary and requested information
to police and other parties involved in the crash.
Do not discuss your personal condition, mental
frame of mind, or anything unrelated to the crash.
This will help guard against post-crash legal action.
If you need roadside assistance, call GM Roadside
Assistance. SeeRoadside Service on page 7-7for
more information.
If your vehicle cannot be driven, know where the
towing service will be taking it. Get a card from the
tow truck operator or write down the driver’s name,
the service’s name, and the phone number.
Remove any valuables from your vehicle before it is
towed away. Make sure this includes your insurance
information and registration if you keep these items
in your vehicle.
Gather the important information you will need from
the other driver. Things like name, address, phone
number, driver’s license number, vehicle license
plate, vehicle make, model and model year, Vehicle
Identi cation Number (VIN), insurance company and
policy number, and a general description of the
damage to the other vehicle.
If possible, call your insurance company from the
scene of the crash. They will walk you through the
information they will need. If they ask for a police
report, phone or go to the police department
headquarters the next day and you can get a copy of
the report for a nominal fee. In some states/provinces
with “no fault” insurance laws, a report may not be
necessary. This is especially true if there are no
injuries and both vehicles are driveable.
Choose a reputable collision repair facility for your
vehicle. Whether you select a GM dealer/retailer or a
private collision repair facility to x the damage,
make sure you are comfortable with them.
Remember, you will have to feel comfortable with
their work for a long time.
Once you have an estimate, read it carefully and
make sure you understand what work will be
performed on your vehicle. If you have a question,
ask for an explanation. Reputable shops welcome
this opportunity.
7-13