2002 GMC ENVOY clock

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.

5-14 How to Add Coolant to the Radiator
1. You can remove the radiator pressure cap when
the cooling system, including the radiator pressure
cap and upper radiator hose, is no longer hot.
Turn the pressure cap slowly counterclockwise about
one full turn.
If you hear a hiss, wait for that to stop. A hiss means
there is still some pressure left.
2. Then keep turning the pressure cap. Remove the
pressure cap.

5-20
1. To remove the underbody-mounted spare, insert the
socket end of the extension, on an angle, into the
hole in the rear bumper. Be sure the socket end of
the extension connects into the hoist shaft.
2. Turn the wheel wrench counterclockwise to lower
the spare tire. Keep turning the wheel wrench
until the spare tire can be pulled out from under
the vehicle.If the spare tire does not lower to the ground, the
secondary latch is engaged causing the tire not to
lower. See ªSecondary Latch Systemº later in
this section.
When the tire has been completely lowered, tilt
the retainer at the end of the cable and pull it through
the wheel opening. Pull the tire out from under
the vehicle.
NOTICE:
To help avoid vehicle damage, do not drive the
vehicle before the cable is properly stored.
3. Put the spare tire near the flat tire.
4. Use the chisel end of the wheel wrench to pry off the
center cap.
See ªRemoving the Flat Tire and Installing the
Spare Tireº later in this section to continue changing
the flat tire.

5-21
Secondary Latch System
The spare tire hoist assembly is equipped with a
secondary latch system. It's designed to stop the spare
tire from suddenly falling off your vehicle. For the
secondary latch to work, the spare tire must be stored
with the valve stem pointing up. See ªStoring a Flat or
Spare Tire and Toolsº in the Index for instructions on
storing the spare tire correctly.
CAUTION:
Before beginning this procedure read all the
instructions. Failure to read and follow the
instructions could damage the hoist assembly and
you and others could get hurt. Read and follow
the instructions listed below.
To release the spare tire from the secondary latch do
the following:
1. Check under the
vehicle to see if the
cable is visible.
2. If it is not visible, proceed to Step 6.
If visible, first try to tighten the cable by turning the
wheel wrench clockwise until you hear two clicks or
feel it skip twice. You cannot overtighten the cable.
3. Loosen the cable by turning the wheel wrench
counterclockwise three or four turns.
4. Repeat this procedure at least two times.
If the spare tire lowers to the ground, continue with
Step 2 of ªRemoving the Spare Tire and Toolsº
earlier in this section.
5. Turn the wrench counterclockwise until
approximately 6 inches (15 cm) of cable is exposed.

5-22
6. Attach the jack handle, extension and the wheel
wrench to the jack and place it under the vehicle
towards the front of the rear bumper. Position the
center lift point of the jack under the center of the
spare tire.
7. Turn the wrench clockwise to raise the jack until it
lifts the end fitting.8. Continue raising the jack until the spare tire stops
moving upward and is held firmly in place. The
secondary latch has released and the spare tire is
balancing on the jack.
9. Lower the jack by turning the wheel wrench
counterclockwise. Keep lowering the jack until
the spare tire slides off the jack or is hanging by
the cable.
CAUTION:
Someone standing too close during the procedure
could be injured by the jack. If the spare tire does
not slide off the jack completely, make sure no
one is behind you or on either side of you as you
pull the jack out from under the spare.
10. Disconnect the jack handle from the jack and
carefully remove the jack. Use one hand to push
against the spare while firmly pulling the jack out
from under the spare tire with the other hand.

5-23
If the spare tire is hanging from the cable, insert the
jack handle, extension and wheel wrench into the
hoist shaft hole in the bumper, on an angle, and turn
the wheel wrench counterclockwise to lower the
spare the rest of the way.11. Tilt the retainer at the end of the cable and pull it
through the wheel opening. Pull the tire out from
under the vehicle.
12. If the cable is hanging under the vehicle, turn the
wheel wrench in the hoist shaft hole in the bumper
clockwise to raise the cable back up.
Have the hoist assembly inspected as soon as you can.
You will not be able to store a spare or flat tire using the
hoist assembly until it has been repaired or replaced.
To continue changing the flat tire, return to Step 2
of ªRemoving the Spare Tire and Toolsº earlier in
this Section.

5-24 Removing the Flat Tire and Installing the
Spare Tire
1. Using the wheel wrench, loosen all the wheel nuts.
Don't remove them yet.
2. Turn the jack adjusting knob clockwise by hand to
raise the jack lift head.
3. Place the handle, extension and wheel wrench onto
the jack.
Front
Rear
A. Frame
B. Jack
C. HandleD. Extension
E. Wheel Wrench

5-25
4. Place the jack in the appropriate position nearest the
flat tire.
CAUTION:
Getting under a vehicle when it is jacked up is
dangerous. If the vehicle slips off the jack, you
could be badly injured or killed. Never get under
a vehicle when it is supported only by a jack.
CAUTION:
Raising your vehicle with the jack improperly
positioned can damage the vehicle and even make
the vehicle fall. To help avoid personal injury and
vehicle damage, be sure to fit the jack lift head
into the proper location before raising the vehicle.
5. Raise the vehicle by turning the jack handle clockwise.
Raise the vehicle far enough off the ground so there is
enough room for the spare tire to fit.
6. Remove all the wheel nuts and take off the flat tire.