air conditioning GMC SIERRA DENALI 2020 Owners Manual

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Introduction 3
Danger, Warning, and
Caution
Warning messages found on vehicle
labels and in this manual describe
hazards and what to do to avoid or
reduce them.
{Danger
Danger indicates a hazard with a
high level of risk which will result
in serious injury or death.
{Warning
Warning indicates a hazard that
could result in injury or death.
Caution
Caution indicates a hazard that
could result in property or vehicle
damage.
A circle with a slash through it is a
safety symbol which means“Do
not,” “Do not do this,” or“Do not let
this happen.”
Symbols
The vehicle has components and
labels that use symbols instead of
text. Symbols are shown along with
the text describing the operation or
information relating to a specific
component, control, message,
gauge, or indicator.
M: Shown when the owner ’s
manual has additional instructions
or information.
*: Shown when the service
manual has additional instructions
or information.
0: Shown when there is more
information on another page —
“see page.” Vehicle Symbol Chart
Here are some additional symbols
that may be found on the vehicle
and what they mean. See the
features in this manual for
information.
u:
Air Conditioning System
G:Air Conditioning Refrigerant Oil
9:Airbag Readiness Light
!:Antilock Brake System (ABS)
$:Brake System Warning Light
9:Dispose of Used Components
Properly
P: Do Not Apply High Pressure
Water
B: Engine Coolant Temperature
_: Flame/Fire Prohibited
H:Flammable
[:Forward Collision Alert
R: Fuse Block Cover Lock
Location
+: Fuses
j:ISOFIX/LATCH System Child
Restraints

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Climate Controls 177
Climate Controls
Climate Control Systems
Climate Control Systems . . . . . 177
Dual Automatic ClimateControl System . . . . . . . . . . . . . 179
Air Vents
Air Vents . . . . . . . . . . . . . . . . . . . . . 182
Maintenance
Passenger Compartment AirFilter . . . . . . . . . . . . . . . . . . . . . . . . 183
Service . . . . . . . . . . . . . . . . . . . . . . . 184
Climate Control Systems
The heating, cooling, and ventilation in the vehicle can be controlled with this
system.
1. Fan Control
2. MAX Defrost
3. Air Delivery Mode Controls
4. A/C (Air Conditioning)
5. TEMP (Temperature Control)
6. Recirculation
7. Rear Window Defogger (If
Equipped) or Heated Mirrors (If
Equipped)9:Turn clockwise or
counterclockwise to increase or
decrease the fan speed. Turn the
knob all the way counterclockwise
to turn the fan off.
TEMP : Turn clockwise or
counterclockwise to increase or
decrease the temperature inside the
vehicle.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
178 Climate Controls
Air Delivery Mode Controls :
Press
z,Y, or[to change the
direction of the airflow. Any
combination of the three controls
can be selected. An indicator light
comes on in the selected mode
button.
To change the current mode, select
one or more of the following. An
indicator light will illuminate:
z: Air is directed to the
windshield, outboard a/c outlets,
and side window outlets.
Y: Air is directed to the a/c outlets.
[:Air is directed to the floor
outlets, with some air directed to the
windshield, outboard a/c outlets,
and side window outlets.
0MAX : Air is directed to the
windshield and the fan runs at a
higher speed if not already above a
medium fan speed. This mode
overrides the previous mode
selected and clears fog or frost from
the windshield more quickly. When the control is pressed again, the
system returns to the previous mode
setting and fan speed.
For best results, clear all snow and
ice from the windshield before
defrosting.
@:
Press to turn on recirculation.
An indicator light comes on. Air is
recirculated to quickly cool the
inside of the vehicle. It can also be
used to help reduce outside air and
odors that enter the vehicle.
Avoid using recirculation for long
periods of time in cold or damp
conditions. Using recirculation in
cold or damp conditions can result
in window fogging.
A/C : Press to turn the air
conditioning on or off. An indicator
light comes on to show that the air
conditioning is enabled. If the fan is
turned off, the air conditioner will not
run. The A/C light will stay on even
if the outside temperatures are
below freezing.
Rear Window Defogger
1REAR : If equipped, press to
turn the rear window defogger on or
off. An indicator light on the button
comes on to show that the rear
window defogger is on.
The rear window defogger only
works when the engine is running.
The defogger turns off if the ignition
is turned off or to ACC/
ACCESSORY.
If equipped with heated outside
mirrors, press
fto turn them on or
off. See Heated Mirrors 043.
Caution
Using a razor blade or sharp
object to clear the inside rear
window can damage the rear
window defogger. Repairs would
not be covered by the vehicle
warranty. Do not clear the inside
rear window with sharp objects.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Climate Controls 179
Dual Automatic Climate Control System
The heating, cooling, and ventilation in the vehicle can be controlled with this
system.
1. Driver and PassengerTemperature Controls
2. MAX Defrost
3. Air Delivery Mode Controls
4. A/C (Air Conditioning)
5. SYNC (Synchronized Temperature) 6. Recirculation
7. Power Button
8. Fan Control
9. Rear Window Defogger (If
Equipped) or Heated Mirrors (If
Equipped)
10. AUTO (Automatic Operation)
Climate Control Display
1. Driver and Passenger Temperature Settings
2. Fan Control
3. Driver and Passenger Temperature Controls
4. Sync (Synchronized Temperature)
5. Recirculation
6. Air Delivery Mode Controls
7. Auto (Automatic Operation)
8. A/C (Air Conditioning)
9. On/Off (Power)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
180 Climate Controls
The fan, air delivery mode, air
conditioning, driver and passenger
temperatures, and Sync settings
can be controlled by touching
CLIMATE on the infotainment Home
Page or the climate button in the
climate control display application
tray. A selection can then be made
on the front climate control page
displayed. See the infotainment
manual.
Climate Control Status Display
The climate control status display
appears briefly when the center
stack climate controls are adjusted.Automatic Operation
The system automatically controls
the fan speed, air delivery, air
conditioning, and recirculation in
order to heat or cool the vehicle to
the desired temperature.
When AUTO is lit, all four functions
operate automatically. Each function
can also be manually set and the
selected setting is displayed.
Functions not manually set will
continue to be automatically
controlled, even if the AUTO
indicator is not lit.
For automatic operation:
1. Press AUTO.
2. Set the temperature. Allow the system time to stabilize. Adjust
the temperature as needed for
best comfort.
To improve fuel efficiency and to
cool the vehicle faster, recirculation
may be automatically selected in
warm weather. The recirculation light will not come
on when automatically controlled.
See
@under
“Manual Operation”
for more details.
Manual Operation
9: Turn clockwise or
counterclockwise to increase or
decrease the fan speed. Press the
knob to turn the fan off. When off is
selected, a small amount of air may
still come out of the outlets
depending on vehicle speed. If any
buttons are pressed or knobs are
turned, the climate control system
will turn on and operate at the
current setting.
Press AUTO to return to automatic
operation.
Driver and Passenger
Temperature Control : The
temperature can be adjusted
separately for the driver and
passenger.
Turn the knob clockwise or
counterclockwise to increase or
decrease the driver or passenger
temperature setting. The driver side

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Climate Controls 181
or passenger side temperature
display shows the temperature
setting increasing or decreasing.
SYNC :Press to link the passenger
temperature setting to the driver
setting. The SYNC indicator light will
turn on. When the passenger setting
is adjusted, the SYNC indicator light
will turn off.
Air Delivery Mode Control : Press
z,Y, or[to change the
direction of the airflow. Any
combination of the three controls
can be selected. An indicator light
comes on in the selected mode
button.
Changing the mode cancels the
automatic operation and the system
goes into manual mode. Press
AUTO to return to automatic
operation.
To change the current mode, select
one or more of the following:
z: Air is directed to the
windshield, outboard a/c outlets,
and side window outlets.
Y: Air is directed to the a/c outlets.
[:Air is directed to the floor
outlets, with some air directed to the
windshield, outboard a/c outlets,
and side window outlets.
0MAX : Air is directed to the
windshield and the fan runs at a
higher speed if not already above a
medium fan speed. This mode
overrides the previous mode
selected and clears fog or frost from
the windshield more quickly. When
the control is pressed again, the
system returns to the previous mode
setting and fan speed.
For best results, clear all snow and
ice from the windshield before
defrosting.
@: Press to turn on recirculation.
An indicator light comes on. Air is
recirculated to quickly cool the
inside of the vehicle. It can also be
used to help reduce outside air and
odors that enter the vehicle. Avoid using recirculation for long
periods of time in cold or damp
conditions. Using recirculation in
cold or damp conditions can result
in window fogging.
A/C :
Press to turn the air
conditioning on or off. An indicator
light comes on to show that the air
conditioning is enabled. If the fan is
turned off, the air conditioner will not
run. The A/C light will stay on even
if the outside temperatures are
below freezing.
Rear Window Defogger
1REAR : If equipped, press to
turn the rear window defogger on or
off. An indicator light on the button
comes on to show that the rear
window defogger is on.
The rear window defogger only
works when the engine is running.
The defogger turns off if the ignition
is turned off or to ACC/
ACCESSORY.
If equipped with heated outside
mirrors, press
fto turn them on or
off. See Heated Mirrors 043.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
184 Climate Controls
3. Press the sides of the glovebox door inward and rotate the
door downward to remove.
4. Pull lever on left side of thefilter door and slide left, then
remove the door. Remove the
old filter.
5. Install the new air filter.
6. Reinstall the filter door.
7. Reverse the steps to reinstall the glove box.
See your dealer if additional
assistance is needed.
Service
All vehicles have a label underhood
that identifies the refrigerant used in
the vehicle. The refrigerant system
should only be serviced by trained
and certified technicians. The air
conditioning evaporator should
never be repaired or replaced by
one from a salvage vehicle.
It should only be replaced by a new
evaporator to ensure proper and
safe operation. During service, all refrigerants
should be reclaimed with proper
equipment. Venting refrigerants
directly to the atmosphere is harmful
to the environment and may also
create unsafe conditions based on
inhalation, combustion, frostbite,
or other health-based concerns.
The air conditioning system requires
periodic maintenance. See
Maintenance Schedule
0441.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 349
Automatic Coolant Service Fill
Instructions (L3B Engine)
See 3.0L Duramax Diesel
supplement for the diesel engine
procedure.
If equipped, this feature assists in
filling and removing air from the
cooling system after service of
components or when coolant is
added after being too low.
To activate the fill and air removal
process:1. With a cold system, add coolant to the indicated mark
on the surge tank.
2. Replace the cap on the surge tank.
3. Connect the vehicle to a battery charger.
4. Set the ignition to Service or Accessory Mode. See Ignition
Positions (Keyless Access)
0 208 or
Ignition Positions (Key Access)
0 210.
5. Turn off the air conditioning. 6. Set the parking brake.
7. At the same time, press the
accelerator and the brake for
automatic transmission
vehicles for two seconds, then
release.
At the end of the cycle, check the
coolant level in the surge tank and
add coolant if it is low. Turn off the
vehicle, allow the Electronic Control
Module (ECM) to go to sleep, about
two minutes, and repeat Steps 3–7.
Listen for pump activation and
movement of the control valves
while watching the level of the
coolant in the surge tank. If the tank
empties, turn the ignition off,
carefully remove the surge tank cap,
refill to the indicated mark, and
repeat Steps 3–6. The fill and air
removal process will run for
approximately 10 minutes.
How to Add Coolant to the
Coolant Surge Tank for
Gasoline Engines Except L3B
If the vehicle has a diesel engine,
see “Cooling System” in the
Duramax diesel supplement for the
proper coolant fill procedure.
{Warning
Spilling coolant on hot engine
parts can burn you. Coolant
contains ethylene glycol and it will
burn if the engine parts are hot
enough.
{Warning
Plain water, or other liquids such
as alcohol, can boil before the
proper coolant mixture will. With
plain water or the wrong mixture,
the engine could get too hot but
there would not be an overheat
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
352 Vehicle Care
If No Steam is Coming from
the Engine Compartment
The ENGINE OVERHEATED STOP
ENGINE or the ENGINE
OVERHEATED IDLE ENGINE
message, along with a low coolant
condition, can indicate a serious
problem.
The 2.7L L4 engine will shut down
automatically if the ENGINE
OVERHEATED STOP ENGINE
message displays.
If there is an engine overheat
warning, but no steam is seen or
heard, the problem may not be too
serious. Sometimes the engine can
get a little too hot when the vehicle:
.Climbs a long hill on a hot day.
. Stops after high-speed driving.
. Idles for long periods in traffic.
. Tows a trailer; see Trailer Towing
0 292. If the ENGINE OVERHEATED
STOP ENGINE or the ENGINE
OVERHEATED IDLE ENGINE
message appears with no sign of
steam, try this for a minute or so:
1. Turn the air conditioning off.
2. Turn the heater on to the highest temperature and to the
highest fan speed. Open the
windows as necessary.
3. When it is safe to do so, pull off the road, shift to P (Park) or
N (Neutral) and let the
engine idle.
If the temperature overheat gauge is
no longer in the overheat zone or an
overheat warning no longer
displays, the vehicle can be driven.
Continue to drive the vehicle slowly
for about 10 minutes. Keep a safe
vehicle distance from the vehicle in
front. If the warning does not come
back on, continue to drive normally
and have the cooling system
checked for proper fill and function.
If the warning continues, pull over,
stop, and park the vehicle
right away. If there is still no sign of steam and
the vehicle is equipped with an
engine driven cooling fan, push
down the accelerator until the
engine speed is about twice as fast
as normal idle speed for at least
five minutes while the vehicle is
parked. If the warning is still there,
turn off the engine and get everyone
out of the vehicle until it cools down.
If there is no sign of steam, idle the
engine for five minutes while
parked. If the warning is still
displayed, turn off the engine until it
cools down.
Overheated Engine
Protection
Operating Mode
If an overheated engine condition
exists and the ENGINE POWER IS
REDUCED message displays, an
overheat protection mode which
alternates firing groups of cylinders
helps to prevent engine damage. In
this mode, a loss in power and
engine performance will be noticed.
This operating mode allows the

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 353
vehicle to be driven to a safe place
in an emergency. Driving extended
distances and/or towing a trailer in
the overheat protection mode
should be avoided.
If the engine or transmission detects
an impending hot fluid condition,
then the transmission may force
upshifts to limit temperatures.
Downshifts may also be prevented
in this instance. Normal operation
may continue unless the display
indicates there is a hot condition
and engine should be idled.
Caution
After driving in the overheated
engine protection operating
mode, the engine oil will be
severely degraded. Any repairs
performed before the engine is
cool may cause engine damage.
Allow the engine to cool before
attempting any repair. Repair the
cause of coolant loss, change the
oil, and reset the oil life system.
SeeEngine Oil 0339.
Engine Fan
If the vehicle has the Duramax
diesel engine, see the Duramax
diesel supplement.
All Engines Except 6.6L
V8 Engine (L8T)
The vehicle has electric cooling
fan(s). The fans may be heard
spinning at low speed during most
everyday driving. The fans may turn
off if no cooling is required. Under
heavy vehicle loading, trailer towing,
high outside temperatures,
or operation of the air conditioning
system, the fans may change to
high speed and an increase in fan
noise may be heard. This is normal
and indicates that the cooling
system is functioning properly. The
fans will change to low speed when
additional cooling is no longer
required.
The electric engine cooling fans
may run after the engine has been
turned off. This is normal and no
service is required.
6.6L V8 Engine (L8T) Only
The vehicle has a clutched engine
cooling fan. When the clutch is
engaged, the fan spins faster to
provide more air to cool the engine.
In most everyday driving conditions,
the fan is spinning slower and the
clutch is not fully engaged. This
improves fuel economy and reduces
fan noise. Under heavy vehicle
loading, trailer towing, and/or high
outside temperatures, the fan speed
increases as the clutch more fully
engages, so an increase in fan
noise may be heard. This is normal
and should not be mistaken as the
transmission slipping or making
extra shifts. It is merely the cooling
system functioning properly. The fan
will slow down when additional
cooling is not required and the
clutch partially disengages.
This fan noise may be heard when
starting the engine. It will go away
as the fan clutch partially
disengages.