2003 GMC ENVOY suspension

After Off-Road Driving
Remove any brush or debris that has collected on the
underbody, chassis or under the hood. These
accumulations can be a ®re hazard.
After operation in mud or sand, have the brake linings
cleaned and checked. These substances can cause
glazing and uneven braking. Check the body structure,
steering, suspension, wheels, tires and exhaust
system for damage. Also, check the fuel lines and
cooling system for any leakage.
Your vehicle will require more frequent service due to
off-road use. Refer to the Maintenance Schedule
for additional information.
Driving at Night
Night driving is more dangerous than day driving.
One reason is that some drivers are likely to be
impaired Ð by alcohol or drugs, with night vision
problems, or by fatigue.
4-28

To ®nd out the actual loads on your front and rear axles,
you need to go to a weigh station and weigh your vehicle.
Your dealer can help you with this. Be sure to spread out
your load equally on both sides of the centerline.
Never exceed the GVWR for your vehicle, or the GAWR
for either the front or rear axle.
If you do have a heavy load, you should spread it out.
Similar appearing vehicles may have different GVWRs
and payloads. Please note your vehicle's
Certi®cation/Tire label or consult your dealer for
additional details.
{CAUTION:
Do not load your vehicle any heavier than the
GVWR, or either the maximum front or rear
GAWR. If you do, parts on your vehicle can
break, and it can change the way your vehicle
handles. These could cause you to lose
control and crash. Also, overloading can
shorten the life of your vehicle.
Using heavier suspension components to get added
durability might not change your vehicle's weight ratings.
Ask your dealer to help you load your vehicle the
right way.
Notice:Your warranty does not cover parts or
components that fail because of overloading.
If you put things inside your vehicle-like suitcases, tools,
packages, or anything else-they will go as fast as the
vehicle goes. If you have to stop or turn quickly, or
if there's a crash, they'll keep going.
{CAUTION:
Things you put inside your vehicle can strike
and injure people in a sudden stop or turn, or
in a crash.
·Put things in the cargo area of your
vehicle. Try to spread the weight evenly.
·Never stack heavier things, like suitcases,
inside the vehicle so that some of them
are above the tops of the seats.
·Don't leave an unsecured child restraint in
your vehicle.
·When you carry something inside the
vehicle, secure it whenever you can.
·Don't leave a seat folded down unless you
need to.
There's also important loading information for off-road
driving in this manual.
4-48

Electronically Controlled Air
Suspension System
Your vehicle may be equipped with an electronically
controlled air suspension system that automatically
keeps your vehicle level as you load and unload. The
system includes a compressor, two height sensors
and two air springs supporting the rear axle.
The system also has an internal clock to prevent
overheating. If the system overheats, all leveling function
stops until the system cools down. During this time,
the indicator light on the air in¯ator system will be
¯ashing.
The ignition has to be on for the system to in¯ate, in
order to raise the vehicle to the standard ride height after
loading. The system can lower the vehicle to the
standard ride height after unloading with the ignition on
and also for up to 30 minutes after the ignition has
been turned off.
You may hear the compressor operating when you load
your vehicle, and periodically as the system adjusts
the vehicle to the standard ride height.Load leveling will not function normally with the in¯ator
hose attached to the in¯ator outlet. Remove the
in¯ator hose from the outlet during loading and
unloading.
If the vehicle is parked for an extended period of time,
some bleed down of the suspension is normal. Upon
starting the vehicle, proper height will be achieved.
Overload Protection
The air suspension system is equipped with overload
protection. Overload protection is designed to protect the
air suspension system, and it is an indicator to the
driver that the vehicle is overloaded. When the overload
protection mode is on, it will not allow damage to the
air compressor. However, do not overload the vehicle.
See
Loading Your Vehicle on page 4-47.
If the suspension remains at a low height, the rear axle
load has exceeded GAWR (Gross Axle Weight
Rating). When the overload protection mode is activated,
the compressor operates for about 30 seconds to one
minute without raising the vehicle depending on the
amount of overload. This will continue each time
the ignition is turned on until the rear axle load is
reduced below GAWR.
4-49

Tire Chains
{CAUTION:
Don't use tire chains. There's not enough
clearance. Tire chains used on a vehicle without
the proper amount of clearance can cause
damage to the brakes, suspension or other
vehicle parts. The area damaged by the tire
chains could cause you to lose control of your
vehicle and you or others may be injured in a
crash. Use another type of traction device only
if its manufacturer recommends it for use on
your vehicle and tire size combination and road
conditions. Follow that manufacturer's
instructions. To help avoid damage to your
vehicle, drive slowly, readjust or remove the
device if it's contacting your vehicle, and don't
spin your wheels. If you do ®nd traction devices
that will ®t, install them on the rear tires.
Accessory In¯ator
Your vehicle may be equipped with an air in¯ator
system. You can in¯ate things like basketballs and
bicycle tires. Also, you can use it to bring your tire
pressure up to the proper pressure. It is not designed to
in¯ate large objects which will require more than ®ve
minutes to in¯ate, such as an air mattress.
The air in¯ator is often
located in the rear
compartment on the
passenger's side of the
vehicle behind an
access cover.
To remove the cover, pull the two tabs on the cover and
pull it off.
5-62

The air in¯ator kit may be located in the glove box. The
kit includes a 22 ft (6.7 m) hose with three nozzle
adapters.
To use the air in¯ator, attach the appropriate nozzle
adapter to the end of the hose if required. Then attach
that end of the hose to the object you wish to in¯ate.
Attach the other end of the hose to the outlet.
Press and release the switch to turn the air in¯ator on.
The indicator light will remain on when the in¯ator is
running.
The system has an internal clock to prevent overheating.
The system will allow about ®ve minutes of running
time, then the compressor will stop. The indicator light
will then begin to ¯ash. When the indicator is off,
the in¯ator can be started again by pressing the switch.
If the compressor is still hot, it may only run for a
short time before shutting off again.
Press and release the switch to turn the in¯ator off.
Place the in¯ator kit tools in the pouch and store
it properly. Remove the in¯ator hose from the outlet
during loading and unloading. Load leveling will
not function with the in¯ator hose attached to the in¯ator
outlet.To reinstall the cover, line up the tabs at the back of the
cover, put it in place and latch the tabs.
A continuous ¯ashing indicator light may also indicate a
malfunction in the air suspension system.
{CAUTION:
In¯ating something too much can make it
explode, and you or others could be injured.
Be sure to read the in¯ator instructions, and
in¯ate any object only to its recommended
pressure.
5-63

Fuses Usage
1Electrically-Controlled Air
Suspension
2Passenger's Side High-Beam
Headlamp
3Passenger's Side Low-Beam
Headlamp
4 Back-Up-Trailer Lamps
5 Driver's Side High-Beam Headlamp
6 Driver's Side Low-Beam Headlamp
7 Wash
8 Automatic Transfer Case
9 Windshield Wipers
10 Powertrain Control Module B
11 Fog Lamps
12 Stop Lamp
13 Cigarette Lighter
14 Ignition Coils
15 Air Suspension Ride
16 TBD-Ignition 1Fuses Usage
17 Crank
18 Air Bag
19 Electric Brake
20 Cooling Fan
21 Horn
22 Ignition E
23 Electronic Throttle Control
24Instrument Panel Cluster, Driver
Information Center
25 Automatic Shift Lock Control System
26 Engine 1
27 Back-Up
28 Powertrain Control Module 1
29 Oxygen Sensor
30 Air Conditioning
31 Truck Body Controller
32 Trailer
33 Anti-Lock Brakes (ABS)
5-93

Fuses Usage
1Electrically-Controlled Air
Suspension
2Passenger's Side High-Beam
Headlamp
3Passenger's Side Low-Beam
Headlamp
4 Back-Up-Trailer Lamps
5 Driver's Side High-Beam Headlamp
6 Driver's Side Low-Beam Headlamp
7 Wash
8 Automatic Transfer Case
9 Windshield Wipers
10 Powertrain Control Module B
11 Fog Lamps
12 Stop Lamp
13 Cigarette Lighter
14 Ignition Coils
15 Cannister Vent
16 TBD-Ignition 1
17 Crank
18 Air Bag
19 Electric Brake
20 Cooling Fan
21 HornFuses Usage
22 Ignition E
23 Electronic Throttle Control
24Instrument Panel Cluster, Driver
Information Center
25 Automatic Shift Lock Control System
26 Engine 1
27 Back-Up
28 Powertrain Control Module 1
30 Air Conditioning
31 Truck Body Controller 1
32 Trailer
33 Anti-Lock Brakes (ABS)
34 Ignition A
35 Blower Motor
36 Ignition B
50 Passenger's Side Trailer Turn
51 Driver's Side Trailer Turn
52 Hazard Flashers
53 Oxygen Sensor Bank A
54 Oxygen Sensor Bank B
55 Injector Bank A
56 Injector Bank B
Relays Usage
37 Headlamp Washer
5-96

Maintenance Schedule......................................6-2
Introduction...................................................6-2
Your Vehicle and the Environment....................6-2
Maintenance Requirements..............................6-2
How This Section is Organized.........................6-3
Part A: Scheduled Maintenance Services...........6-4
Using Your Maintenance Schedule....................6-4
Scheduled Maintenance...................................6-5
Part B: Owner Checks and Services................6-11
At Each Fuel Fill..........................................6-11
At Least Once a Month.................................6-11
At Least Twice a Year...................................6-12At Least Once a Year...................................6-13
Part C: Periodic MaintenanceInspections.........6-16
Steering, Suspension and Front Drive Axle
Boot and Seal Inspection............................6-16
Exhaust System Inspection............................6-16
Fuel System Inspection..................................6-16
Engine Cooling System Inspection...................6-17
Transfer Case and Front Axle (Four-Wheel
Drive) Inspection.......................................6-17
Brake System Inspection................................6-17
Part D: Recommended Fluids and Lubricants. . . .6-18
Part E: Maintenance Record...........................6-20
Section 6 Maintenance Schedule
6-1