2002 GMC ENVOY service indicator

2-28
4HI: Use 4HI when you need extra traction, such as
on snowy or icy roads or in most off
-road situations.
This setting also engages your front axle to help drive
your vehicle.
4LO: This setting also engages your front axle and
delivers extra torque. You may never need 4LO. It sends
maximum power to all four wheels. You might choose
4LO if you are driving off
-road in deep sand, deep mud,
and climbing or descending steep hills.
CAUTION:
Shifting the transfer case to NEUTRAL can
cause your vehicle to roll even if the transmission
is in PARK (P). You or someone else could be
seriously injured. Be sure to set the parking
brake before placing the transfer case in
NEUTRAL. See ªParking Brakeº in the Index.
NEUTRAL: Shift the vehicle's transfer case
to NEUTRAL only when towing your vehicle.
See ªRecreational Vehicle Towingº in the Index
for more information.
An indicator light in the knob will show you which
position the transfer case is in. The indicator lights will
come on briefly when you turn on the ignition and one
will stay on. If the lights do not come on, you should
take your vehicle to your dealer for service. An indicator
light will flash while shifting the transfer case. It will
remain illuminated 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 SERVICE 4WD light on the instrument panel
cluster stays on, you should take your vehicle to your
dealer for service. See ªService 4WDº in the Index for
further information.

2-82
Malfunction Indicator Lamp (Service
Engine Soon Light in the United States
or Check Engine Light in Canada)
United States Canada
Your vehicle is equipped with a computer which
monitors operation of the fuel, ignition and emission
control systems.This system is called OBD II (On
-Board
Diagnostics
-Second Generation) and is intended to assure
that emissions are at acceptable levels for the life of the
vehicle, helping to produce a cleaner environment. The
SERVICE ENGINE SOON or CHECK ENGINE light
comes on to indicate that there is a problem and service is
required. Malfunctions often will be indicated by the
system before any problem is apparent. This may prevent
more serious damage to your vehicle. This system is also
designed to assist your service technician in correctly
diagnosing any malfunction.
NOTICE:
If you keep driving your vehicle with this light
on, after a while, your emission controls may not
work as well, your fuel economy may not be as
good and your engine may not run as smoothly.
This could lead to costly repairs that may not be
covered by your warranty.

3-62
After you clean the player, press and hold the eject
(upward pointing triangle) button for five seconds to
reset the CLEAN PLAYR indicator. The radio will
display CLEANED to show the indicator was reset.
Cassettes are subject to wear and the sound quality
may degrade over time. Always make sure the cassette
tape is in good condition before you have your tape
player serviced.
Care of Your Compact Disc and
DVD Player
The use of CD lens cleaner discs is not advised, due to
the risk of contaminating the lens of the CD optics with
lubricants internal to the CD mechanism.
Care of Your Compact Discs and DVDs
Handle discs carefully. Store them in their original cases
or other protective cases and away from direct sunlight
and dust. If the surface of a disc is soiled, dampen a
clean, soft cloth in a mild, neutral detergent solution
and clean it, wiping from the center to the edge.
Be sure never to touch the side without writing when
handling discs. Pick up discs by grasping the outer
edges or the edge of the hole and the outer edge.
Cleaning the Video Screen
Pour some isopropyl or rubbing alcohol on a clean cloth
and gently wipe the video screen. Do not spray directly
onto the screen and do not press too hard or too long on
the video screen.

4-49 Electronically Controlled Air Suspension
System (If Equipped)
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 inflator system
will be flashing.
The ignition has to be on for the system to inflate, 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
inflator hose attached to the inflator outlet. Remove
the inflator hose from the outlet during loading
and unloading.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 ªLoading Your Vehicleº earlier in this section.
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.
Indicator Light
The indicator light on the inflator switch in the rear
passenger compartment also serves as an indicator for
internal system error. If the indicator light is flashing
without the load leveling function or the inflator being
active, turn off the ignition. The next day turn on the
ignition and check the indicator light. The vehicle can
be driven with the light flashing, but if it is you should
have the vehicle serviced as soon as possible.

6-5 Additives
Some gasolines that are not reformulated for low
emissions may contain an octane
-enhancing additive
called methylcyclopentadienyl manganese tricarbonyl
(MMT); ask the attendant where you buy gasoline
whether the fuel contains MMT. General Motors does
not recommend the use of such gasolines. Fuels
containing MMT can reduce the life of spark plugs and
the performance of the emission control system may be
affected. The malfunction indicator lamp may turn on.
If this occurs, return to your authorized GM dealer
for service.
To provide cleaner air, all gasolines in the United States
are now required to contain additives that will help
prevent engine and fuel system deposits from forming,
allowing your emission control system to work properly.
You should not have to add anything to your fuel.
Gasolines containing oxygenates, such as ethers and
ethanol, and reformulated gasolines may be available
in your area to contribute to clean air. General Motors
recommends that you use these gasolines, particularly
if they comply with the specifications described earlier.
NOTICE:
Your vehicle was not designed for fuel that
contains methanol. Don't use fuel containing
methanol. It can corrode metal parts in your
fuel system and also damage plastic and rubber
parts. That damage wouldn't be covered under
your warranty.
Fuels in Foreign Countries
If you plan on driving in another country outside the
United States or Canada, the proper fuel may be hard
to find. Never use leaded gasoline or any other fuel not
recommended in the previous text on fuel. Costly repairs
caused by use of improper fuel wouldn't be covered by
your warranty.
To check on fuel availability, ask an auto club, or
contact a major oil company that does business in the
country where you'll be driving.

6-16
Engine Air Cleaner/Filter
The engine air cleaner/filter
is located toward the front
of the engine compartment
on the passenger's side of
the vehicle.
See ªEngine Compartment Overviewº in the Index for
more information on engine air cleaner/filter location.
The engine air cleaner/filter
assembly has an indicator
that lets you know when the
air filter is dirty and needs
to be serviced. The indicator
is located on the engine
air cleaner/filter air duct.
See ªEngine Compartment Overviewº in the Index
for more information on engine air cleaner/filter
indicator location.
The service window (A) with the percentage scale
shows the amount of engine air cleaner/filter life used.
When both service window (A) and service window (B)
turn orange, replace the engine air cleaner/filter.

6-17
After changing the engine air cleaner/filter, press the
button on top of the indicator to reset it.
See ªOwner Checks and Servicesº in the Index to
determine when to check the indicator.
To replace the engine air cleaner/filter, do the following:
1. Remove the three screws on the engine air
cleaner/filter and lift off the cover.
2. Twist out the old engine air cleaner/filter and replace
it with a new one.
3. Reinstall the cover.
CAUTION:
Operating the engine with the air cleaner/filter
off can cause you or others to be burned. The air
cleaner not only cleans the air, it stops flame if
the engine backfires. If it isn't there, and the
engine backfires, you could be burned. Don't
drive with it off, and be careful working on the
engine with the air cleaner/filter off.
NOTICE:
If the air cleaner/filter is off, a backfire can
cause a damaging engine fire. And, dirt can easily
get into your engine, which will damage it.
Always have the air cleaner/filter in place when
you're driving.

6-31
NOTICE:

Using the wrong fluid can badly damage
brake system parts. For example, just a few
drops of mineral
-based oil, such as engine
oil, in your brake system can damage brake
system parts so badly that they'll have to be
replaced. Don't let someone put in the
wrong kind of fluid.

If you spill brake fluid on your vehicle's
painted surfaces, the paint finish can be
damaged. Be careful not to spill brake fluid
on your vehicle. If you do, wash it off
immediately. See ªAppearance Careº in
the Index.
Brake Wear
Your vehicle has four-wheel disc brakes.
Disc brake pads have built
-in wear indicators that make a
high
-pitched warning sound when the brake pads are
worn and new pads are needed. The sound may come and
go or be heard all the time your vehicle is moving (except
when you are pushing on the brake pedal firmly).
CAUTION:
The brake wear warning sound means that soon
your brakes won't work well. That could lead to
an accident. When you hear the brake wear
warning sound, have your vehicle serviced.
NOTICE:
Continuing to drive with worn-out brake pads
could result in costly brake repair.
Some driving conditions or climates may cause a brake
squeal when the brakes are first applied or lightly
applied. This does not mean something is wrong with
your brakes.