2001 GMC YUKON tow

2-79
NOTICE:
Modifications made to the engine, transmission,
exhaust or fuel system of your vehicle or the
replacement of the original tires with other
than those of the same Tire Performance
Criteria (TPC) can affect your vehicle's emission
controls and may cause the SERVICE ENGINE
SOON or CHECK ENGINE light to come on.
Modifications to these systems could lead to
costly repairs not covered by your warranty. This
may also result in a failure to pass a required
Emission Inspection/Maintenance test.
This light should come on, as a check to show you it is
working, when the ignition is on and the engine is not
running. If the light doesn't come on, have it repaired.
This light will also come on during a malfunction in one
of two ways:

Light Flashing
-- A misfire condition has been
detected. A misfire increases vehicle emissions and
may damage the emission control system on your
vehicle. Dealer or qualified service center diagnosis
and service may be required.
Light On Steady
-- An emission control system
malfunction has been detected on your vehicle.
Dealer or qualified service center diagnosis and
service may be required.
If the Light Is Flashing
The following may prevent more serious damage to
your vehicle:

Reducing vehicle speed.

Avoiding hard accelerations.

Avoiding steep uphill grades.

If you are towing a trailer, reduce the amount of
cargo being hauled as soon as it is possible.
If the light stops flashing and remains on steady, see
ªIf the Light Is On Steadyº following.
If the light continues to flash, when it is safe to do so,
stop the vehicle. Find a safe place to park your vehicle.
Turn the key off, wait at least 10 seconds and restart the
engine. If the light remains on steady, see ªIf the Light
Is On Steadyº following. If the light is still flashing,
follow the previous steps, and drive the vehicle to your
dealer or qualified service center for service.

2-83 Cruise Light (If Equipped)
United States Canada
The CRUISE light comes on whenever you set your
cruise control. See ªCruise Controlº in the Index.
Tow/Haul Light
This message is displayed
when the tow/haul mode has
been activated.
For more information, see ªTow/Haul Modeº in
the Index.

2-86
The following situations can cause the transmission to
operate at higher temperatures:

Towing a trailer

Hot outside air temperatures

Hauling a large or heavy load

Low transmission fluid level

High transmission fluid level

Restricted air flow to the radiator and the auxiliary
transmission oil cooler (if equipped).
A temporary solution to hotter transmission operating
temperatures may be to let the transmission cool down.
If the transmission is operated at higher temperatures on
a frequent basis, see ªScheduled Maintenanceº in the
Index for the proper transmission maintenance intervals.
Trans Hot...Idle Engine
Your vehicle has a transmission over-temperature
display contained in the message center.
If this warning message is
displayed, pull the vehicle
off the roadway when it is
safe to do so.
Set the parking brake and place the transmission in
PARK (P). Idle the engine until the message center no
longer displays a message. If idling the engine does not turn
the warning message off after 10 to 15 minutes, contact
your nearest dealer or the GM Roadside Assistance Center.
See ªRoadside Assistanceº in the Index.
NOTICE:
If you keep driving your vehicle with the
transmission TRANS HOT...IDLE ENGINE
message displayed, you can damage the
transmission. This could lead to costly repairs
that may not be covered under your warranty.

2-87
The following situations can cause the transmission to
operate at higher temperatures:

Towing a trailer

Hot outside air temperatures

Hauling a heavy load

Low transmission fluid level

High transmission fluid level

Restricted air flow to the radiator and the auxiliary
transmission oil cooler (if equipped).
A temporary solution to hotter transmission operating
temperatures may be to let the transmission cool down.
If the transmission is operated at higher temperatures on
a frequent basis, see ªScheduled Maintenanceº in the
Index for the proper transmission maintenance intervals.
Low Coolant
This message is displayed
when the cooling system is
low on coolant.
The engine may overheat. See ªEngine Coolantº in the
Index and have your vehicle serviced as soon as you can.
Check Coolant Temp
This message is displayed
when the cooling system
temperature gets hot.
Check the coolant temperature gage and the coolant
level. See ªEngine Coolantº and ªEngine Coolant
Temperature Gageº in the Index. See ªEngine
Overheatingº in the Index for further information.
Engine Overheated
This message is displayed
when the cooling system
temperature gets too hot.
This message will be displayed after the air conditioning
system has automatically turned off for the engine
coolant protection mode. See ªEngine Overheatingº in
the Index for further information.

3-2
Comfort Controls
Standard Comfort Controls
Fan Knob
The knob on the left side of the control panel adjusts the
fan speed. To increase airflow, turn the knob clockwise.
To decrease airflow, turn it counterclockwise. To turn
the fan off, turn the knob to OFF.
Temperature Knob
The middle knob on the control panel lets you select the
temperature of the air flowing into the passenger area.
Turn the knob clockwise toward the red area for warmer
air. Turn the knob counterclockwise toward the blue area
for cooler air.Mode Knob
The right knob on the control panel allows you to
choose the direction of air delivery.
VENT: This setting directs the air through the
instrument panel outlets.
BI-LEVEL: Air is delivered through the
heater floor outlets as well as the instrument panel
outlets. The air flow can be divided between VENT
and HEATER depending upon where the knob is
placed between the settings.
HEATER: This setting directs most of the
warmed air through the heater floor outlets, and the
rest of the air is divided between the windshield
defroster outlets and the side window defroster outlets.
BLEND: Airflow is delivered through the heater
floor outlets, the windshield defroster outlets and the
side window defroster outlets. The air flow can be
divided between HEATER and DEFROST depending
upon where the knob is placed between the settings.
DEFROST: This setting directs most air through
the windshield defroster outlets, side window defroster
outlets and some through the heater outlets.

3-3 Heater and Air Conditioning Comfort
Controls (If Equipped)
Fan Knob
The knob on the left side of the control panel adjusts the
fan speed. To increase airflow, turn the knob clockwise.
To decrease airflow, turn it counterclockwise. To turn
the fan off, turn the knob to OFF.
Temperature Knob
The middle knob on the control panel lets you select the
temperature of the air flowing into the passenger area.
Turn the knob clockwise toward the red area for warmer
air. Turn the knob counterclockwise toward the blue area
for cooler air.Mode Knob
The right knob on the control panel allows you to
choose the direction of air delivery.
PANEL: This setting directs the air through the
instrument panel outlets.
BI-LEVEL: Air is delivered through the
instrument panel outlets and the heater floor outlets.
The air flow can be divided between PANEL and
HEATER depending upon where the knob is placed
between the settings. Pressing the A/C button while
in this mode causes cooler air to come out of the
instrument panel outlets and warmer air to come
out of the heater floor outlets.
HEATER: This setting directs most of the
warmed air through the heater floor outlets as well as
some air through the windshield defroster outlets and
side window defroster outlets.
BLEND: Airflow is delivered through the heater
floor outlets, the windshield defroster outlets and the
side window defroster outlets. The air flow can be
divided between HEATER and DEFROST depending
upon where the knob is placed between the settings.
The air conditioning compressor may run to dehumidify
the air to prevent window fogging.

3-5 Electronic Climate Control System
(If Equipped)
Fan Control
The knob on the left side of the electronic climate control
panel controls the fan speed. To manually increase airflow,
move the knob clockwise. To manually decrease airflow,
move it counterclockwise.
OFF: If the knob is in OFF, outside air will still enter
the vehicle, and will be directed based on the position of
the mode knob.
AUTO: If the knob is in AUTO, the fan speed will vary
as the system maintains the selected temperature.When both the fan control and mode knobs are in the
AUTO position, the system will then automatically
maintain the desired cabin temperature as selected by
the temperature knob. Manual control of functions is
also available.
Temperature Knob
The middle knob on the control panel lets you select
the desired air temperature in your vehicle. This knob
will allow you to adjust the interior air temperature
independent of the function knob setting. Move the
knob clockwise toward 82 for warmer air. Move the
knob counterclockwise toward 66 for cooler air. When
the system is set for automatic operation, sensors will
control the fan/blower speed.
Full Hot: If you turn the temperature knob past
82
F (28
C), the system will go into the ªfull hotº
mode. The system will remain at that maximum heating
setting and the fan will blow at the speed the fan knob is
set to. If the fan is in AUTO, it will run at full speed.
Full Cold: If you turn the temperature knob past
66
F (19
C), the system will go into the ªfull coldº
mode. The system will remain at that maximum cooling
setting and the fan will blow at the speed the fan knob is
set to. If the fan is in AUTO, it will run at full speed.

3-8
Air conditioning will be automatically disabled when
the outside temperature drops below a level at which
air conditioning is ineffective.
Remember that in order for the automatic system to perform
well, it needs A/C to provide cooling performance.
Rear Air Conditioning and Heating Systems
(If Equipped)
If your vehicle has one of these systems, you can increase
and decrease the airflow at the rear vents. Depending on
the system you have and the setting selected, you can
send cooled or heated air to the rear of the vehicle.
Rear Air Conditioning (Without Rear Heater)
(If Equipped)
Front ControlTo increase and decrease the flow of cooled air to the
rear vents, turn the knob to the blower speed you want.
The knob has three speed positions. To increase the flow
of cooled air, turn the switch toward ª3º. To decrease
the flow of cooled air, turn it toward ª1º. To turn the
fan off, turn the knob to OFF.
To operate the rear system using the front control,
just turn the knob to the blower position you want.
Rear Control
To use the rear control, first turn the front control to
REAR. Then, the rear control can be used to increase
and decrease the airflow.