2003 GMC ENVOY engine

Engine Coolant Heater
Your vehicle may have this feature. In very cold
weather, 0ÉF (-18ÉC) or colder, the engine coolant
heater can help. You'll get easier starting and better fuel
economy during engine warm-up. Usually, the coolant
heater should be plugged in a minimum of four
hours prior to starting your vehicle. At temperatures
above 32ÉF (0ÉC), use of the coolant heater is not
required.
To Use the Engine Coolant Heater
1. Turn off the engine.
2. Open the hood and unwrap the electrical cord. The
cord is located on the driver's side of the engine
compartment, behind the battery.
3. Plug it into a normal, grounded 110-Volt AC outlet.
{CAUTION:
Plugging the cord into an ungrounded outlet
could cause an electrical shock. Also, the
wrong kind of extension cord could overheat
and cause a ®re. You could be seriously
injured. Plug the cord into a properly grounded
three-prong 110-volt AC outlet. If the cord
won't reach, use a heavy-duty three-prong
extension cord rated for at least 15 amps.
4. Before starting the engine, be sure to unplug and
store the cord as it was before to keep it away
from moving engine parts. If you don't, it could be
damaged.
How long should you keep the coolant heater plugged
in? The answer depends on the outside temperature, the
kind of oil you have, and some other things. Instead
of trying to list everything here, we ask that you contact
your dealer in the area where you'll be parking your
vehicle. The dealer can give you the best advice for that
particular area.
2-22

Automatic Transmission Operation
There are several different positions for your gear
shift lever.
PARK (P):This position locks the rear wheels. It's the
best position to use when you start the engine
because your vehicle can't move easily.
{CAUTION:
It is dangerous to get out of your vehicle if the
shift lever is not fully in PARK (P) with the
parking brake ®rmly set. Your vehicle can roll.
Don't leave your vehicle when the engine is
running unless you have to. If you have left the
engine running, the vehicle can move
suddenly. You or others could be injured. To
be sure your vehicle won't move, even when
you're on fairly level ground, always set your
parking brake and move the shift lever to
PARK (P). See ªShifting Into Park (P)º in the
Index. If you're pulling a trailer, see ªTowing a
Trailerº in the Index.
{CAUTION:
If you have four-wheel drive, your vehicle will
be free to roll Ð even if your shift lever is in
PARK (P) Ð if your transfer case is in
NEUTRAL. So, be sure the transfer case is in a
drive gear Ð not in NEUTRAL. See
ªFour-Wheel Drive (Automatic Transfer Case)º
in the Index. See ªShifting Into Park (P)º in
the Index.
Ensure the shift lever is fully in PARK (P) before starting
the engine. Your vehicle has an automatic transmission
shift lock control system. You have to fully apply the
regular brakes before you can shift from PARK (P) when
the ignition key is in RUN. If you cannot shift out of
PARK (P), ease pressure on the shift lever, press the
button on the shift lever and push the shift lever all
the way into PARK (P) as you maintain brake
application. Move the shift lever into the gear you wish.
See
Shifting Out of Park (P) on page 2-31.
2-23

REVERSE (R):Use this gear to back up.
Notice:Shifting to REVERSE (R) while your vehicle
is moving forward could damage your transmission.
Shift to REVERSE (R) only after your vehicle is
stopped.
To rock your vehicle back and forth to get out of snow,
ice or sand without damaging your transmission,
see If You Are Stuck: In Sand, Mud, Ice or Snow on
page 4-44.
NEUTRAL (N):In this position, the engine doesn't
connect with the wheels. To restart when you're already
moving, use NEUTRAL (N) only.
{CAUTION:
Shifting into a drive gear while your engine is
ªracingº (running at high speed) is dangerous.
Unless your foot is ®rmly on the brake pedal,
your vehicle could move very rapidly. You
could lose control and hit people or objects.
Don't shift into a drive gear while your engine
is racing.
Notice:Damage to your transmission caused by
shifting out of PARK (P) or NEUTRAL (N) with
the engine racing isn't covered by your warranty.On cold days, about 32É F (0ÉC) or colder, your
transmission is designed to shift differently until the
engine reaches normal operating temperature. This is
intended to improve heater performance.
DRIVE (D):This position is for normal driving. If you
need more power for passing, and you're:
·Going less than about 35 mph (55 km/h), push the
accelerator pedal about halfway down.
·Going about 35 mph (55 km/h) or more, push the
accelerator all the way down.
You'll shift down to the next gear and have more power.
DRIVE (D) can be used when towing a trailer, carrying
a heavy load, driving on steep hills or for off-road driving.
You may want to shift the transmission to THIRD (3)
or, if necessary, a lower gear selection if the
transmission shifts too often.
THIRD (3):This position is also used for normal driving.
However, it offers more power and lower fuel economy
than DRIVE (D).
SECOND (2):This position gives you more power but
lower fuel economy than THIRD (3). You can use
SECOND (2) on hills. It can help control your speed as
you go down steep mountain roads, but then you
would also want to use the brakes off and on.
You can also use SECOND (2) for starting the vehicle
from a stop on slippery road surfaces.
2-24

FIRST (1):This position gives you even more power
but lower fuel economy than SECOND (2). You can use
it on very steep hills, or in deep snow or mud. If the
selector lever is put in FIRST (1) while the vehicle
is moving forward, the transmission won't shift into ®rst
gear until the vehicle is going slowly enough.
Notice:If your wheels won't turn, don't try to drive.
This might happen if you were stuck in very deep
sand or mud or were up against a solid object. You
could damage your transmission. Also, if you
stop when going uphill, don't hold your vehicle there
with only the accelerator pedal. This could overheat
and damage the transmission. Use your brakes
or shift into PARK (P) to hold your vehicle in
position on a hill.
Four-Wheel Drive
If your vehicle has four-wheel drive, you can send your
engine's driving power to all four wheels for extra
traction. To get the most satisfaction out of four-wheel
drive, you must be familiar with its operation. Read
the part that follows before using four-wheel drive. You
should use two-wheel drive high (2HI) for most
normal driving conditions.
Notice:Driving in the 4-WHEEL HIGH (4HI) or
4-WHEEL LOW (4LO) positions for a long time on
dry or wet pavement could shorten the life of
your vehicle's drivetrain.
Automatic Transfer Case
If your vehicle is equipped
with four-wheel drive, the
transfer case knob is
located to the right of the
steering wheel on the
instrument panel. Use this
knob to shift into and
out of four-wheel drive.
2HI (Two-Wheel High):This setting is for driving in
most street and highway situations. Your front axle is not
engaged in two-wheel drive. It also provides the best
fuel economy.
A4WD (Automatic Four-Wheel Drive):This setting is
ideal for use when road conditions are variable.
When driving your vehicle in A4WD, 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.
2-25

Shifting into 4LO
To shift to 4LO, the vehicle's engine must be running
and the vehicle must be stopped or moving less
than 2 mph (3.2 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). Turn the knob to 4LO. You must wait for
the 4LO indicator light to stop ¯ashing and remain
illuminated before shifting your transmission into gear.
If you turn the knob to 4LO when your vehicle is in gear
and/or moving, the 4LO indicator light will ¯ash for
30 seconds and not complete the shift unless your
vehicle is moving less than 2 mph (3.2 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, A4WD or 2HI your vehicle
must be stopped or moving less than 2 mph (3.2 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). Turn the knob to 4HI, A4WD or 2HI. You
must wait for the 4HI, A4WD or 2HI indicator light to stop
¯ashing and remain illuminated before shifting your
transmission into gear.If the knob is turned to 4HI, A4WD or 2HI when your
vehicle is in gear and/or moving, the 4HI, A4WD or 2HI
indicator light will ¯ash for 30 seconds. It will not
complete the shift unless your vehicle is moving less
than 2 mph (3.2 km/h) with the transmission in
NEUTRAL (N).
Shifting into NEUTRAL
Before shifting the transfer case to NEUTRAL, ®rst
make sure the vehicle is parked so that it will not roll.
1. Set the parking brake.
2. Start the vehicle.
3. Put the transmission in NEUTRAL (N).
4. Shift the transfer case to 2HI.
5. Turn the transfer case knob all of the way past 4LO
and hold it there for a minimum of 10 seconds. The
neutral indicator light will come on.
6. Shift the transmission to REVERSE (R) for one
second, then shift the transmission to DRIVE (D)
for one second.
7. Place the transmission shift lever in PARK (P).
8. Release the parking brake prior to towing.
9. Turn the ignition to LOCK.
2-27

Notice:Driving with the parking brake on can
cause your parking brake to overheat. You may have
to replace them, and you could also damage other
parts of your vehicle.
If you are towing a trailer and you must park on a hill,
see
Towing a Trailer on page 4-50. That section
shows what to do ®rst to keep the trailer from moving.
Shifting Into Park (P)
{CAUTION:
It can be dangerous to get out of your vehicle
if the shift lever is not fully in PARK (P) with
the parking brake ®rmly set. Your vehicle can
roll. If you have left the engine running, the
vehicle can move suddenly. You or others
could be injured. To be sure your vehicle won't
move, even when you're on fairly level ground,
CAUTION: (Continued)
CAUTION: (Continued)
use the steps that follow. With four-wheel
drive, your vehicle will be free to roll Ð even if
your shift lever is in PARK (P) Ð if your
transfer case is in NEUTRAL. So, be sure the
transfer case is in a drive gear Ð not in
NEUTRAL. See ªFour-Wheel Driveº in the
Index. Always put the shift lever fully in
PARK (P) with the parking brake ®rmly set. If
you're pulling a trailer, see ªTowing a Trailerº
in the Index.
To shift into PARK (P), do the following:
1. Hold the brake pedal down with your right foot and
set the parking brake.
2-29

2. Move the shift lever into PARK (P) like this:
2.1. Press the button in on the side of the lever.
2.2. Push the lever all the way toward the
front of the vehicle.
3. Turn the ignition key to LOCK.
4. Remove the key and take it with you. You know
your vehicle is in PARK (P) if the key can be
removed from the ignition.Leaving Your Vehicle With the Engine
Running
{CAUTION:
It can be dangerous to leave your vehicle
with the engine running. Your vehicle could
move suddenly if the shift lever is not fully in
PARK (P) with the parking brake ®rmly set.
If you have four-wheel drive, your vehicle
will be free to roll ± even if your lever is in
PARK (P) ± if your transfer case is in
NEUTRAL. So be sure the transfer case is in a
drive gear ± not NEUTRAL. See ªFour-Wheel
Drive (Automatic Transfer Case)º in the Index.
And, if you leave the vehicle with the engine
running, it could overheat and even catch ®re.
You or others could be injured. Don't leave
your vehicle with the engine running unless
you have to.
2-30

If you have to leave your vehicle with the engine
running, be sure your vehicle is in PARK (P) and your
parking brake is ®rmly set before you leave it. After
you've moved the shift lever into PARK (P), hold
the regular brake pedal down. Then, see if you can
move the shift lever away from PARK (P) without ®rst
pressing the button on the console shift lever. If you can,
it means that the shift lever wasn't fully locked into
PARK (P).
Torque Lock
If you are parking on a hill and you don't shift your
transmission into PARK (P) properly, the weight of the
vehicle may put too much force on the parking pawl
in the transmission. You may ®nd it difficult to pull the
shift lever out of PARK (P). This is called ªtorque
lock.º To prevent torque lock, set the parking brake and
then shift into PARK (P) properly before you leave
the driver's seat. To ®nd out how, see
Shifting Into
Park (P) on page 2-29.When you are ready to drive, move the shift lever out of
PARK (P)
beforeyou release the parking brake.
If torque lock does occur, you may need to have another
vehicle push yours a little uphill to take some of the
pressure from the parking pawl in the transmission, so
you can pull the shift lever out of PARK (P).
Shifting Out of Park (P)
Your vehicle has an automatic transmission shift lock
control system. You have to fully apply the regular
brakes before you can shift from PARK (P) when the
ignition is in RUN. See
Automatic Transmission
Operation on page 2-23.
2-31