1999 GMC ENVOY 4WD

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2-23
AUTO 4WD: This setting is ideal for use when road
conditions are variable. When driving your vehicle in
AUTO 4WD, the front axle is engaged, but the vehicle's
power is sent to the rear wheels. When the vehicle
senses a loss of traction, the system will automatically
engage four
-wheel drive. Driving in this mode results in
slightly lower fuel economy than 2HI.
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.
NEUTRAL: Shift the vehicle's transfer case to
NEUTRAL only when towing your vehicle. See
ªRecreational Vehicle Towingº or ªTowing Your
Vehicleº in the Index for more information.
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.
Indicator lights in the switches show which setting you
are 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 stays on, you should take
your vehicle to your dealer for service. See ªService
4WDº in the Index for further information.
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2-24
Shifting to 4HI or AUTO 4WD
Press and release the 4HI or AUTO 4WD switch. This
can be done at any speed and the indicator light will
flash while shifting. It will remain illuminated when the
shift is complete.
Shifting to 2HI
Press and release the 2HI switch. This can be done at
any speed.
Shifting to 4LO
To shift to 4LO, the vehicle's engine must be running
and the vehicle must be stopped or moving less than 3
mph (4.8 km/h) with the transmission in NEUTRAL
(N). The preferred method for shifting into 4LO is to
have your vehicle moving 1 or 2 mph (1.6 to 3.2 km/h).
Press and release the 4LO switch. You must wait for the
4LO indicator light to stop flashing and remain
illuminated before shifting your transmission into gear.
If the 4LO switch is pressed when your vehicle is in
gear and/or moving, the 4LO indicator light will flash
for 30 seconds and not complete the shift unless your
vehicle is moving less than 3 mph (4.8 km/h) and the
transmission is in NEUTRAL (N). After 30 seconds, the
transfer case will return to the setting last chosen.Shifting Out of 4LO
To shift from 4LO to 4HI, AUTO 4WD or 2HI your
vehicle must be stopped or moving less than 3 mph
(4.8 km/h) with the transmission in NEUTRAL (N) and
the engine running. The preferred method for shifting
out of 4LO is to have your vehicle moving 1 or 2 mph
(1.6 to 3.2 km/h). Press and release the 4HI, AUTO
4WD or 2HI switch. You must wait for the 4HI, AUTO
4WD or 2HI indicator light to stop flashing and remain
illuminated before shifting your transmission into gear.
If the 4HI, AUTO 4WD or 2HI switch is pressed when
your vehicle is in gear and/or moving, the 4HI, AUTO
4WD or 2HI indicator light will flash for 30 seconds but
will not complete the shift unless your vehicle is moving
less than 3 mph (4.8 km/h) with the transmission in
NEUTRAL (N).
Shifting to NEUTRAL
To shift the transfer case to NEUTRAL first make sure
the vehicle is parked so that it will not roll:
1. Set the parking brake.
2. Start the vehicle.
3. Connect the vehicle to the towing vehicle.
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2-25
4. Put the transmission in NEUTRAL (N).
5. Shift the transfer case to 2HI.
6. Simultaneously press and hold the 2HI and 4LO
buttons for 10 seconds. The red NEUTRAL light
will come on when the transfer case shift to
NEUTRAL is complete.
7. Shift the transmission to REVERSE (R) for one
second, then shift the transmission to DRIVE (D)
for one second.
8. Turn the ignition to OFF.
9. Place the transmission shift lever to PARK (P).
10. Release the parking brake prior to towing.
Shifting Out of NEUTRAL
To shift out of NEUTRAL:
1. Set the parking brake and apply the regular
brake pedal.
2. Start the vehicle with the transmission in PARK (P).3. Press the button for the desired transfer case shift
position (2HI, 4HI, AUTO 4WD or 4LO).
4. Put the transmission in NEUTRAL (N).
5. Shift the transmission lever to the desired position.
After the transfer case has shifted out of NEUTRAL,
the red light will go out.
6. A re
-engagement sound is normal when shifting out
of NEUTRAL.
Parking Brake
To set the parking brake, hold the regular brake pedal
down with your right foot. Push down the parking brake
pedal with your left foot. If the ignition is on, the brake
system warning light will come on.
To release the parking brake, hold the regular brake
pedal down.
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2-74 Security Warning Light
This light will come on
briefly when you turn the
key toward START. The
light will stay on until the
engine starts.
If the light flashes, the Passlock

system has entered a
tamper mode. If the vehicle fails to start, see ªPasslockº
in the Index.
If the light comes on continuously while driving and
stays on, there may be a problem with the Passlock
system. Your vehicle will not be protected by Passlock,
and you should see your dealer.
This light should also flash as you open the door (if your
ignition is off). This is a reminder to activate the
theft
-deterrent system. See ªContent Theft-Deterrentº in
the Index for more information.
Service Four-Wheel-Drive Warning Light
Your vehicle is equipped with the Automatic
Four
-Wheel-Drive Transfer Case. It has a computer
which controls the four
-wheel-drive system.
This light should come on
briefly when you turn on the
ignition, as a check to show
you it is working.
The SERVICE 4WD light comes on to indicate that
there may be a problem with the Automatic Four
-Wheel
Drive system and service is required. Malfunctions can
be indicated by the system before any problem is
apparent, which may prevent serious damage to the
vehicle. This system is also designed to assist your
service technician in correctly diagnosing a malfunction.
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6-57
Fuse/Circuit
BreakerUsage
14 Power Locks Motor
15 4WD Switch, Engine Controls
(VCM, PCM, Transmission)
16 Air Bag
17 Front Wiper
18 Steering Wheel Audio Controls
19 Radio, Battery
20 Amplifier
21 HVAC I (Automatic),
HVAC Sensors (Automatic)
22 Anti
-Lock Brakes
23 Rear Wiper
24 Radio, Ignition
Engine Compartment Fuse Block
The fuse block is under the hood at the driver's side of
the engine compartment.
Remove the cover by turning the fastener
counterclockwise. To reinstall the fuse panel cover, push
in and turn the fastener clockwise.
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9-6
Lights
Air Bag Readiness 1-22, 2-67 . . . . . . . . . . . . . . . . . . . . . . .
Anti-Lock Brake System Warning 2-69, 4-7 . . . . . . . . . . . .
Brake System Warning 2-68 . . . . . . . . . . . . . . . . . . . . . . . . .
Charging System 2-67 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Check Gages 2-75 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gate Ajar 2-75 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low Fuel 2-76 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety Belt Reminder 1-8, 2-66 . . . . . . . . . . . . . . . . . . . . . .
Security Warning 2-74 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service 4WD 2-74 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service Engine Soon 2-70 . . . . . . . . . . . . . . . . . . . . . . . . . .
Loading Your Vehicle 4-41 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loading Your Vehicle for Off-Road Driving 4-15 . . . . . . . . . .
Locking Rear Axle 2-32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lockout Prevention 2-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lockout Switch 2-32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Locks 2-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Door 2-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Transmission Check 7-42 . . . . . . . . . . . . . . . . . . . .
Key Lock Cylinder Service 7-40 . . . . . . . . . . . . . . . . . . . . .
Power Door 2-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rear Door Security 2-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loss of Control 4-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low Fuel Light 2-76 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lubricants and Fluids 7-45 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lubrication Service, Body 7-40 . . . . . . . . . . . . . . . . . . . . . . . .
Luggage Carrier 2-53 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lumbar Controls 1-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maintenance Record 7-47 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maintenance Schedule 7-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Long Trip/Highway 7-6, 7-27 . . . . . . . . . . . . . . . . . . . . . . . Owner Checks and Services 7
-39 . . . . . . . . . . . . . . . . . . . . .
Periodic Maintenance Inspections 7-43 . . . . . . . . . . . . . . . .
Recommended Fluids and Lubricants 7-45 . . . . . . . . . . . . .
Scheduled Maintenance Services 7-4 . . . . . . . . . . . . . . . . . .
Short Trip/City 7-5, 7-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maintenance, Underbody 6-52 . . . . . . . . . . . . . . . . . . . . . . . . .
Maintenance When Trailer Towing 4-54 . . . . . . . . . . . . . . . . .
Malfunction Indicator Lamp 2-70 . . . . . . . . . . . . . . . . . . . . . .
Memory Seat 1-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Methanol 6-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mirrors 2-44 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Convex Outside 2-45 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrochromic Day/Night Inside Rearview 2-44 . . . . . . . .
Heated Outside Rearview 2-45 . . . . . . . . . . . . . . . . . . . . . . .
Illuminated Visor Vanity 2-55 . . . . . . . . . . . . . . . . . . . . . . .
Outside 2-45 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Folding 2-46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Model Reference iii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mountain Roads 4
-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Multifunction Lever 2-33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Net, Convenience 2-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Neutral 2-19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
New Vehicle ªBreak-Inº 2-13 . . . . . . . . . . . . . . . . . . . . . . . . .
Night Vision 4-27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Normal Maintenance Replacement Parts 6-61 . . . . . . . . . . . . .
Odometer 2-65 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Off-Road Driving with Your Four-Wheel-Drive
Vehicle 4-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Off-Road Recovery 4-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil, Engine 6-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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9-8
Recommended Fluids and Lubricants 7-45 . . . . . . . . . . . . . . .
Recovery Hooks 5-31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recovery Tank, Coolant 5-12 . . . . . . . . . . . . . . . . . . . . . . . . . .
Recreational Vehicle Towing 4-39 . . . . . . . . . . . . . . . . . . . . . .
Replacement
Bulbs 6
-60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts 6-61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wheel 6-43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reporting Safety Defects 8-10 . . . . . . . . . . . . . . . . . . . . . . . . .
Restraints
Check 7
-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Checking 1-52 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Child 1-38 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Head 1-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replacing Parts After a Crash 1-53 . . . . . . . . . . . . . . . . . . .
Retained Accessory Power 2-15 . . . . . . . . . . . . . . . . . . . . . . . .
Reverse 2-19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Right Front Passenger Position 1-20 . . . . . . . . . . . . . . . . . . . .
Roadside Assistance 8-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Roadside Assistance Canadian 8-7 . . . . . . . . . . . . . . . . . . . . . .
Rocking Your Vehicle 5-31 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rotation, Tires 6-39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety Belts 1-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adults 1-12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Care 6-48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Center Rear Passenger Position 1-34 . . . . . . . . . . . . . . . . . .
Children 1-35, 1-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Driver Position 1-12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Extender 1-52 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
How to Wear Properly 1-12 . . . . . . . . . . . . . . . . . . . . . . . . .
Lap Belt 1-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lap-Shoulder 1-13, 1-28 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Questions and Answers 1-11 . . . . . . . . . . . . . . . . . . . . . . . . Rear Comfort Guides 1
-31 . . . . . . . . . . . . . . . . . . . . . . . . . .
Rear Seat Outside Passengers 1-28 . . . . . . . . . . . . . . . . . . .
Replacing After a Crash 1-53 . . . . . . . . . . . . . . . . . . . . . . . .
Right Front Passenger Position 1-20 . . . . . . . . . . . . . . . . . .
Use During Pregnancy 1-19 . . . . . . . . . . . . . . . . . . . . . . . . .
Why They Work 1-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety Chains 4-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety Defects, Reporting 8-10 . . . . . . . . . . . . . . . . . . . . . . . .
Safety Warnings and Symbols iii. . . . . . . . . . . . . . . . . . . . . . .
Scheduled Maintenance Services 7
-4 . . . . . . . . . . . . . . . . . . . .
Seats 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Heated Front 1-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lumbar Controls 1-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Memory 1-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rear 1-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reclining Front 1-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Seats and Restraint Systems 1-1 . . . . . . . . . . . . . . . . . . . . . . . .
Second Gear 2-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Security Warning Light 2-74 . . . . . . . . . . . . . . . . . . . . . . . . . .
Service 4WD Light 2-74 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service and Appearance Care 6-1 . . . . . . . . . . . . . . . . . . . . . .
Service and Owner Publications 8-12, 8-13 . . . . . . . . . . . . . .
Service Engine Soon Light 2-70 . . . . . . . . . . . . . . . . . . . . . . .
Service Parts Identification Label 6-54 . . . . . . . . . . . . . . . . . .
Service Work, Doing Your Own 6-2 . . . . . . . . . . . . . . . . . . . .
Servicing Your Air Bag-Equipped Vehicle 1-27 . . . . . . . . . . .
Sheet Metal Damage 6-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shifting 2-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Into Park 2-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Out of Park 2-28 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Signaling Turns 2-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Skidding 4-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications and Capacities 6-60 . . . . . . . . . . . . . . . . . . . . . .
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