ECU GMC ENVOY DENALI 2009 Workshop Manual

Look in the following chart to nd the maximum trailer weight for the vehicle.
Vehicle Axle Ratio Max. Trailer Wt. *GCWR
2WD Envoy (4.2 L L6 Engine)3.42 5,300 lbs (2 404 kg) 10,000 lbs (4 536 kg)
3.73 5,800 lbs (2 631 kg) 10,500 lbs (4 763 kg)
4.10 6,300 lbs (2 858 kg) 11,000 lbs (4 990 kg)
2WD Envoy (5.3 L V8 Engine)3.42 6,100 lbs (2 767 kg) 11,000 lbs (4 990 kg)
3.73 6,600 lbs (2 994 kg) 11,500 lbs (5 216 kg)
4WD Envoy (4.2 L L6 Engine)3.42 5,200 lbs (2 359 kg) 10,000 lbs (4 536 kg)
3.73 5,700 lbs (2 858 kg) 10,500 lbs (4 763 kg)
4.10 6,200 lbs (2 812 kg) 11,000 lbs (4 990 kg)
4WD Envoy (5.3 L V8 Engine)3.42 6,000 lbs (2 721 kg) 11,000 lbs (4 990 kg)
3.73 6,500 lbs (2 948 kg) 11,500 lbs (5 216 kg)
*The Gross Combination Weight Rating (GCWR) is the total allowable weight of the completely loaded vehicle and
trailer including any passengers, cargo, equipment and conversion. The GCWR for the vehicle should not be
exceeded.
Ask your dealer for our trailering information or advice, or write us at our Customer Assistance Offices. SeeCustomer
Assistance Offices on page 7-6for more information.
4-48

Driving with a Trailer
{CAUTION:
When towing a trailer, exhaust gases may collect
at the rear of the vehicle and enter if the liftgate,
trunk/hatch, or rear-most window is open.
Engine exhaust contains carbon monoxide (CO)
which cannot be seen or smelled. It can cause
unconsciousness and even death.
To maximize safety when towing a trailer:
Have the exhaust system inspected for leaks
and make necessary repairs before starting
a trip.
Never drive with the liftgate, trunk/hatch, or
rear-most window open.
Fully open the air outlets on or under the
instrument panel.
Adjust the Climate Control system to a setting
that brings in only outside air and set the fan
speed to the highest setting. See Climate
Control System in the Index.
For more information about carbon monoxide, see
Engine Exhaust on page 2-37.Towing a trailer requires a certain amount of experience.
Get to know the rig before setting out for the open road.
Get acquainted with the feel of handling and braking with
the added weight of the trailer. And always keep in mind
that the vehicle you are driving is now longer and not as
responsive as the vehicle is by itself.
Before starting, check all trailer hitch parts and
attachments, safety chains, electrical connectors, lamps,
tires and mirror adjustments. If the trailer has electric
brakes, start the vehicle and trailer moving and then
apply the trailer brake controller by hand to be sure the
brakes are working. This checks the electrical connection
at the same time.
During the trip, check occasionally to be sure that the
load is secure, and that the lamps and any trailer brakes
are still working.
Following Distance
Stay at least twice as far behind the vehicle ahead as
you would when driving the vehicle without a trailer.
This can help to avoid situations that require heavy
braking and sudden turns.
Passing
More passing distance is needed when towing a trailer.
Because the rig is longer, it is necessary to go much
farther beyond the passed vehicle before returning to
the lane.
4-53

6. Start the engine and let it run until you can feel the
upper radiator hose getting hot. Watch out for the
engine cooling fan.
7. By this time, the coolant level inside the radiator
ller neck may be lower. If the level is lower, add
more of the proper DEX-COOL coolant mixture
through the ller neck until the level reaches
the base of the ller neck.8. Then replace the pressure cap. At any time during
this procedure if coolant begins to ow out of the
ller neck, reinstall the pressure cap. Be sure
the pressure cap is hand-tight and fully seated.
Notice:If the pressure cap is not tightly installed,
coolant loss and possible engine damage may occur.
Be sure the cap is properly and tightly secured.
Engine Overheating
The vehicle has several indicators to warn of engine
overheating.
You will nd a coolant temperature gage on the vehicle’s
instrument panel. SeeEngine Coolant Temperature
Gage on page 3-37for more information.
If the vehicle has a Driver Information Center (DIC), the
display will show an Engine Coolant Hot/Engine
Overheated message. SeeDIC Warnings and Messages
on page 3-51for more information.
5-30

Bulb Replacement
For the proper type of replacement bulbs, see
Replacement Bulbs on page 5-49.
For any bulb changing procedure not listed in this
section, contact your dealer/retailer.
Halogen Bulbs
{CAUTION:
Halogen bulbs have pressurized gas inside and
can burst if you drop or scratch the bulb. You or
others could be injured. Be sure to read and follow
the instructions on the bulb package.
Headlamps
To replace one of these bulbs:
1. Open the hood.Hood Release on page 5-11.
2. Lift the two headlamp retaining clips.3. Pull the headlamp assembly away from the vehicle
to access the electrical connectors.
4. Remove the cover from the headlamp bulb.
5. Turn the bulb socket counterclockwise and remove it.
6. Disconnect the electrical connector from the old bulb.
7. Plug the electrical connector into the new bulb using
care not to touch the glass with your ngers.
8. Turn the socket clockwise to reinstall it.
9. Reinstall the headlamp cover.
10. Push the headlamp assembly toward the vehicle.
11. Press down on the headlamp retaining clips to
secure the headlamp assembly.
5-46

Front Turn Signal, Sidemarker and
Parking Lamps
To replace one of these bulbs:
1. Follow Steps 1 through 3 underHeadlamps on
page 5-46to access the front turn signal,
sidemarker or parking lamp.
2. Turn the bulb socket counterclockwise and remove
it from the lamp assembly.
3. Holding the socket, pull the old bulb to release it
from the socket.
4. Push the new bulb into the socket until it clicks.
5. Insert the bulb socket into the lamp assembly and
turn it clockwise to secure.
6. Reinstall the headlamp assembly by lining up the
headlamp assembly with the slots in the headlamp
retaining clips.
7. Press down on the headlamp retaining clips to
secure the headlamp assembly.
Taillamps, Turn Signal, and
Stoplamps
To replace a stoplamp/taillamp or turn signal bulb:
1. Open the liftgate. SeeLiftgate/Liftglass on
page 2-12.
2. Remove the
two screws from
the taillamp
assembly.
3. Pull the assembly away from the vehicle.
5-47

4. Unclip the wiring harness (A) and remove the three
socket retaining screws (B).
5. Remove the socket plate.
6. Holding the socket, pull the bulb to straight out
release it from the socket.
7. Push the new bulb into the socket until it clicks.
8. Reinstall the socket plate and three screws.
9. Reconnect the wiring harness.
10. Reinstall the taillamp assembly by lining up the
locator pins with the retainers in the body of the
vehicle.
11. Reinstall the two screws.
Back-Up Lamps
The back-up lamps are located in the rear bumper.
To replace a bulb:
1. Reach behind the rear bumper and locate the bulb
socket.
2. Turn it counterclockwise to remove from the lamp
assembly.
3. Holding the socket, pull the old bulb to release it
from the socket.
4. Push in a new bulb into the bulb socket until it
clicks.
5. Reinstall the bulb socket into the lamp assembly
and turn it clockwise to secure.
5-48

{CAUTION:
Rust or dirt on a wheel, or on the parts to
which it is fastened, can make wheel nuts
become loose after time. The wheel could
come off and cause an accident. When you
change a wheel, remove any rust or dirt from
places where the wheel attaches to the
vehicle. In an emergency, you can use a
cloth or a paper towel to do this; but be sure
to use a scraper or wire brush later, if
needed, to get all the rust or dirt off. See
Changing a Flat Tire on page 5-88.
Make sure the spare tire, if the vehicle has one, is
stored securely. Push, pull, and then try to rotate or
turn the tire. If it moves, tighten the cable. See
Storing a Flat or Spare Tire and Tools on
page 5-100.
When It Is Time for New Tires
Various factors, such as maintenance, temperatures,
driving speeds, vehicle loading, and road conditions,
inuence when you need new tires.
One way to tell when it is
time for new tires is to
check the treadwear
indicators, which appear
when your tires have only
1/16 inch (1.6 mm) or less
of tread remaining. Some
commercial truck tires
may not have treadwear
indicators.
5-69

Follow this diagram to store the underbody-mounted at
or spare tire.
A. Wheel Wrench
B. Hoist Shaft
C. Extension
D. Retainer
E. Spare or Flat Tire
(Valve Stem
Pointed Up)
1. Put the tire (E) on the ground at the rear of the
vehicle.
2. Remove the hubcap, if the vehicle has one, from the
at tire by tapping the backside of the hubcap with
the wheel wrench (A). Store in a safe location until
the at tire is repaired. Once the tire is repaired,
replace the hubcap.
3. Make sure the valve stem is pointed up and to
the rear.
4. Pull the retainer (D) through the wheel.
5. Put the socket end of the extension (C) through the
hole just above the rear bumper at a 45 degree
angle downward. Connect the socket end of
the extension to the hoist shaft (B).6. Raise the tire fully against the underside of the
vehicle. Continue turning the wheel wrench (A)
clockwise until you hear two clicks or feel it skip
twice. This indicates that the tire is secure and the
cable is tight. The spare tire hoist cannot be
overtightened.
7. Make sure the tire is stored securely. Push, pull (A),
and then try to turn (B) the tire. If the tire moves,
use the wheel wrench and socket end of the
extension to tighten the cable.
8. Return the equipment to the proper location in the
vehicle as shown next.
5-101

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 5-25.
Windshield Washer Fluid Level Check
Check the windshield washer uid level in the windshield
washer uid reservoir and add the proper uid if
necessary.
At Least Once a Month
Tire Ination Check
Inspect the vehicle’s tires and make sure they are
inated to the correct pressures. Do not forget to
check the spare tire, if the vehicle has one. See
Inflation - Tire Pressure on page 5-60. If the vehicle
has a spare tire, check to make sure it is stored
securely. SeeChanging a Flat Tire on page 5-88.
Tire Wear Inspection
Tire rotation may be required for high mileage highway
drivers prior to the Engine Oil Life System service
notication. Check the tires for wear and, if necessary,
rotate the tires. SeeTire Inspection and Rotation on
page 5-68.
6-9

Calling for Assistance
When calling Roadside Assistance, have the following
information ready:
Your name, home address, and home telephone
number
Telephone number of your location
Location of the vehicle
Model, year, color, and license plate number of the
vehicle
Odometer reading, Vehicle Identication Number
(VIN), and delivery date of the vehicle
Description of the problem
Coverage
Services are provided up to 5 years/100,000 miles
(160 000 km), whichever comes rst.
In the U.S., anyone driving the vehicle is covered.
In Canada, a person driving the vehicle without
permission from the owner is not covered.
Roadside Assistance is not a part of the New Vehicle
Limited Warranty. GMC and General Motors of Canada
Limited reserve the right to make any changes or
discontinue the Roadside Assistance program at any
time without notication.GMC and General Motors of Canada Limited reserve the
right to limit services or payment to an owner or driver if
they decide the claims are made too often, or the same
type of claim is made many times.
Services Provided
Emergency Fuel Delivery:Delivery of enough fuel
for the vehicle to get to the nearest service station.
Lock-Out Service:Service is provided to unlock the
vehicle if you are locked out. A remote unlock may
be available if you have OnStar
®. For security
reasons, the driver must present identication
before this service is given.
Emergency Tow From a Public Road or
Highway:Tow to the nearest GMC dealer for
warranty service, or if the vehicle was in a crash
and cannot be driven. Assistance is also given when
the vehicle is stuck in the sand, mud, or snow.
Flat Tire Change:Service is provided to change a
at tire with the spare tire. The spare tire, if equipped,
must be in good condition and properly inated.
It is the owner’s responsibility for the repair or
replacement of the tire if it is not covered by the
warranty.
Battery Jump Start:Service is provided to jump
start a dead battery.
7-8