
Windshield Wipers
You control the windshield
wipers by turning the band
with the wiper symbol
on it.
9(Off):Turn the band on the lever to this symbol to
turn off the windshield wipers.
8(Mist):For a single wiping cycle, turn the band to
this symbol. Hold it there until the wipers start, then
let go. The wipers will stop after one cycle. If you want
more cycles, hold the band on mist longer.
You can set the wiper speed for a long or short delay
between wipes. This can be very useful in light rain
or snow. Turn the band to select the delay time.
The farther the band is turned upward, the longer the
delay will be. The farther the band is turned downward,
the shorter the delay will be.For steady wiping at low speed, turn the band toward
you to the first solid band below the delay settings.
For high-speed wiping, turn the band farther, to the last
solid band below the delay settings. To stop the
wipers, move the band to off.
Be sure to clear ice and snow from the wiper blades
before using them. If they are frozen to the windshield,
carefully loosen or thaw them. If your blades do
become worn or damaged, get new blades or blade
inserts. For more information, seeWindshield Wiper
Blade Replacement on page 5-65.
Heavy snow or ice can overload your wipers. The
windshield wiper motor is protected from overload by a
circuit breaker and a fuse. If the motor overheats
due to heavy snow or ice the wiper will stop until the
motor cools. Although the circuit is protected from
electrical overload, overload due to heavy snow or ice
may cause wiper linkage damage. Always clear ice and
heavy snow from the windshield before using your
windshield wipers.
3-9

Exterior Lamps
The control located to the left of the steering column
operates the exterior lamps.
The exterior lamp control has three positions:
OFF:Turning the control to this position turns off all
lamps except the Daytime Running Lamps (DRL).
;(Parking Lamps):Turning the control to this
position turns on the parking lamps, together with
the following:
•Marker Lamps
•Taillamps
•License Plate Lamps
•Instrument Panel Lights
O(Headlamps):Turning the control to this position
turns on the headlamps, together with the previously
listed lamps and lights.
You can switch your headlamps from low to high beam
by pulling the turn signal/multifunction lever toward
you. Pull the lever toward you again to return to
low beam.
A circuit breaker protects your headlamps. If you have
an electrical overload, your headlamps will flicker on and
off. Have your headlamp wiring checked right away if
this ever happens.
3-14

)(Bi-Level):This mode directs half of the air to the
instrument panel vents, then directs the remaining
air to the floor vents. Cooler air is directed to the upper
vents and warmer air to the floor vents.
6(Floor):This mode directs most of the air to the
floor vents. Use this mode to send air to the rear of the
vehicle. Keep the area under the front seats free of
objects that could obstruct airflow to the rear of
the vehicle.
The mode knob can also be used to select the defrost
mode. For more information, see “Defogging and
Defrosting” later in this section.
9(Fan):Turn the left knob clockwise or
counterclockwise to increase or decrease the fan speed.
To increase airflow, turn the knob clockwise. To
decrease airflow, turn it counterclockwise. To turn the
fan off, turn the mode knob on the far right
counterclockwise to the off position.
Temperature Knob:Turn the middle knob located
clockwise or counterclockwise to increase or decrease
the temperature inside of your vehicle. Turn the
knob toward the red area for warmer air. Turn the knob
toward the blue area for cooler air.If your vehicle has air conditioning, the controls will look
like this:
On hot days, open the windows to let hot inside air
escape; then close them. This helps to reduce the time
it takes for your vehicle to cool down. It also helps
the system to operate more efficiently.
<(Maximum Air Conditioning):Turn the right knob
to this setting for maximum cooling. This setting puts
the system in recirculation mode and helps to maximize
your air conditioner’s performance and your vehicle’s
fuel economy. This setting also cools the air the fastest.
Y(Air Conditioning):This setting is used for
normal cooling on hot days. It cools outside air and
directs it through the instrument panel vents.
)(Bi-Level Air Conditioning):This setting divides
airflow between the floor vents and instrument panel
vents. The air conditioning compressor will cycle
continuously in this setting as long as the outside
temperature is warm enough to activate the compressor.Vehicles With Air Conditioning
3-21

Defogging and Defrosting
Fog on the inside of windows is a result of high humidity
(moisture) condensing on the cool window glass. This
can be minimized if the climate control is used properly.
There are two modes to clear fog or frost from your
windshield and side windows.
Use the defog mode to clear the windows of fog or
moisture and warm the passengers. Use the defrost
mode to remove fog or frost from the windshield more
quickly. For best results, clear all snow and ice from the
windshield before defrosting.
Turn the mode knob on the right of the climate control
panel to select the defog or defrost mode.
-(Defog):With this setting, the outside air comes out
of both the floor and defroster outlets. Adjust the
temperature knob for warmer or cooler air. The air
conditioning compressor may operate in this setting to
dehumidify the air.
0(Defrost):This setting operates the defroster. Most
of the air comes out near the windshield, with some
going to the floor outlets and front side windows. The air
conditioning compressor may operate in this setting to
dehumidify the air.The defog setting is useful for cold weather with a large
number of passengers or very humid conditions to
help keep the windshield clear. Use defrost to remove
fog or ice from the windshield quickly in extremely
cold conditions. The temperature knob should be in the
red area and the fan control toward high. Do not
drive the vehicle until all the windows are clear.
Rear Window Defogger
The rear window defogger uses a warming grid to
remove fog or frost from the rear window.
Be sure to clear as much snow from the rear window as
possible.
Press this button which is
located near the fan
control to turn the rear
window defogger on or off.
An indicator light in the
button will come on when
the rear window defogger
is working.
The rear window defogger will only work when the
ignition is in RUN.
3-22

Service Transmission Warning Light
If your vehicle has an Allison automatic transmission,
certain transmission malfunctions will turn this light on.
This light is located with
the auxiliary warning lights
in the center of the
instrument panel.
If this light comes on while you are driving, do not use
the transmission shift control or you may lose forward
gears. The computer for the transmission senses
a problem and chooses a gear to stay in so that you
can drive the vehicle in that gear. You may not be able
to drive as fast or back up when this light is on.
Notice:If you continue driving your vehicle after
the transmission warning light comes on, you could
damage the transmission. While this light is on,
the transmission cannot operate in all gears. If you
attempt to shift gears, the vehicle may not
continue to move. Do not attempt to shift gears
while the transmission warning light is on. Instead,
drive directly to a GM dealer for service. If you
cannot drive to a dealer immediately, have the
vehicle towed.
Range Inhibit Warning Indicator
If your vehicle has an Allison
1000/2000/2200/2400/2500 series automatic
transmission, a lighted bar under the current gear
selected will flash.
If your vehicle has an Allison 3000/3500 series automatic
transmission, the current gear selected on the pushbutton
display will flash.
The flashing bar or gear selection indicates that
transmission range shifts may not occur.
For detailed information on shift inhibit limitations, see
the Allison Automatic Transmission Operator’s Manual in
your vehicle for further information.
Brake System Warning Light
Your vehicle has either hydraulic or air brakes. Each
system has different warning lights.
3-31

Hydraulic Brake System
Warning Lights
Vehicles with hydraulic brake systems have two brake
system warning lights on the instrument panel.
If the BRAKE system
warning light comes on, it
means that the fluid
level in the master cylinder
reservoir is low or there
is another problem
with your hydraulic brakes.
When it comes on, you will also hear a warning tone.
The BRAKE system warning light may come on, and the
warning tone may sound, when you’re turning and
braking at the same time. This is normal. See “Hydraulic
Brake Systems” underBraking on page 4-5.If the service brakes soon
warning light comes on, it
means there may be
something wrong in the
brake system.
When this light comes on, you will also hear a warning
tone. Have the system repaired immediately.
Both of these lights should come on briefly every time
you start your engine. If they don’t come on then,
have them fixed so they will be ready to warn you if
there’s a problem. If one or both of these warning lights
stay on after you start the engine, there could be a
brake problem. Have your brake system inspected
right away.
If one or both of these lights come on while you are
driving, pull off the road and stop carefully. You
may notice that the pedal is harder to push, or the pedal
may go closer to the floor. It may take longer to stop.
If the BRAKE light is still on, have the vehicle towed for
service. SeeTowing Your Vehicle on page 4-35. See
“Hydraulic Brake Systems” underBraking on page 4-5
for further information.
3-32

Wait to Start Indicator
(Diesel Engine)
If your vehicle has the DURAMAX®6600, you will have
glow plugs. If your vehicle has the DURAMAX®7800,
you will have glow plugs and an inlet heater. If your
vehicle has a Caterpillar
®engine, you will have an
inlet heater.
The light in the center of
the instrument panel will
come on when the
inlet heater is on and the
ignition key is in RUN.
Wait until the indicator light turns off before turning the
ignition key to START.
Malfunction Indicator Lamp
Service Engine Soon Light
If this light comes on or
flashes while you are
driving, two things
may happen.
First, you will not notice any difference in engine
performance, but your tail pipe emissions may increase.
Second, your engine may not run properly or may
stall without warning. If either of these things happen,
drive or tow your vehicle to your dealer for service.
This light should come on when the ignition is on, but
the engine is not running, as a check to show you
it is working. If it does not come on at all, have
it repaired.
Notice:If you keep driving your vehicle with this
light on, after awhile, 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.
3-36

To adjust both tone controls and both speaker controls
to the middle position, first end out of audio mode
by pressing another button, causing the radio to perform
that function or by waiting five seconds for the display
to return to time of day. Then press and hold AUDIO for
more than two seconds until you hear a beep. CEN
will appear on the display.
Adjusting the Speakers (Balance/Fade)
AUDIO:To adjust the balance between the right
and the left speakers, press and release AUDIO until
BAL appears on the display. Then press and hold the up
or the down arrow to move the sound toward the right
or the left speakers.
To adjust the fade between the front and the rear
speakers, press and release AUDIO until FAD appears
on the display. Then press and hold the up or the
down arrow to move the sound toward the front or the
rear speakers.
To adjust balance or fade to the middle position, select
BAL or FAD. Then press and hold AUDIO for more
than two seconds until you hear a beep. L (balance) and
a zero or F and a zero will appear on the display.To adjust both tone controls and both speaker controls
to the middle position, first end out of audio mode
by pressing another button, causing the radio to perform
that function or by waiting five seconds for the display
to return to time of day. Then press and hold AUDIO for
more than two seconds until you hear a beep. CEN
will appear on the display.
Fade may not be available if the vehicle is a regular
cab model.Radio Messages
CAL (Calibrated):The audio system has been
calibrated for your vehicle from the factory. If CAL
appears on the display it means that the radio has not
been configured properly for your vehicle and must
be returned to your GM dealer for service.
LOC (Locked):This message is displayed when the
THEFTLOCK
®system has locked up. Take the vehicle
to your GM dealer for service.
If any error occurs repeatedly or if an error cannot be
corrected, contact your GM dealer.
3-47