2021 GMC SIERRA ignition position

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 245
Caution
Shifting the transmission into gear before
the requested mode indicator light has
stopped flashing could damage the
transfer case.
If the transmission is not shifted into
N (Neutral) or the vehicle has not slowed to
5 km/h (3 mph) within 20 seconds, the
transfer case will remain in its original state.
This will be indicated in the instrument
cluster.
With the vehicle moving less than 5 km/h
(3 mph), and the transmission in N (Neutral),
attempt the shift again.
Shifting Into N (Neutral)
To shift into N (Neutral): 1. Start the vehicle.
2. Shift the transmission to N (Neutral).
3. Shift the transfer case to 2
m.
4. Apply the parking brake and/or brake pedal.
5. Press 2
mfive times in 10 seconds until
the N (Neutral) graphic starts flashing in
the instrument cluster. When the shift is
complete, the graphic stops flashing. If the parking brake and/or brake pedal
is not applied within 20 seconds, the
transfer case will remain in the original
state.
6. If the transmission is not shifted into N (Neutral) or the vehicle has not slowed
to 5 km/h (3 mph) within 20 seconds,
the transfer case will remain in its
original state. This will be indicated in
the instrument cluster.
Shifting Out of N (Neutral)
To shift out of N (Neutral): 1. Turn the ignition on with the engine off. See Ignition Positions (Keyless Access)
0 230 or
Ignition Positions (Key Access) 0229.
2. Set the parking brake. See Electric
Parking Brake 0247.
3. Shift the transmission to N (Neutral).
4. Shift the transfer case to 2
m. Transfer
case shifts out of N (Neutral) can only be
made into 2
m. When the shift to 2mis
complete, the graphic in the instrument
cluster will stop flashing. If the transfer
case cannot complete a shift, the graphic
will return to the previously selected
setting. Single Speed Transfer Case
If equipped, the transfer case controls are
used to shift into and out of four-wheel
drive.
To shift the transfer case, press the desired
button. The graphic in the instrument
cluster will flash while a shift is in progress.
The graphic displayed will change to indicate
the setting requested.
When the shift is complete the graphic will
stop flashing. The DIC message turns off
once the shift is complete. If the transfer
case cannot complete a shift request, it will
go back to its last chosen setting.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 321
Vehicle Care
General Information
General Information . . . . . . . . . . . . . . . . . . . 322
California Proposition 65 Warning . . . . . 322
California Perchlorate MaterialsRequirements . . . . . . . . . . . . . . . . . . . . . . . . 322
Accessories and Modifications . . . . . . . . . 323
Vehicle Checks
Doing Your Own Service Work . . . . . . . . . 323
Hood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
Engine Compartment Overview . . . . . . . . 325
Engine Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
Engine Oil Life System . . . . . . . . . . . . . . . . . 332
Automatic Transmission Fluid . . . . . . . . . . 333
Engine Air Filter Life System . . . . . . . . . . . 333
Engine Air Cleaner/Filter . . . . . . . . . . . . . . . 334
Cooling System . . . . . . . . . . . . . . . . . . . . . . . . 335
Engine Overheating . . . . . . . . . . . . . . . . . . . 338
Overheated Engine Protection Operating Mode . . . . . . . . . . . . . . . . . . . . . 340
Engine Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
Washer Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . 340
Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
Brake Pad Life System . . . . . . . . . . . . . . . . . 342
Brake Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
Battery - North America . . . . . . . . . . . . . . . 343 Four-Wheel Drive . . . . . . . . . . . . . . . . . . . . . . 346
Front Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
Rear Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
Starter Switch Check . . . . . . . . . . . . . . . . . . 347
Automatic Transmission Shift Lock
Control Function Check . . . . . . . . . . . . . . 347
Ignition Transmission Lock Check . . . . . . 347
Park Brake and P (Park) Mechanism Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
Wiper Blade Replacement . . . . . . . . . . . . . 348
Glass Replacement . . . . . . . . . . . . . . . . . . . . 348
Windshield Replacement . . . . . . . . . . . . . . 348
Gas Strut(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
Headlamp Aiming
Front Headlamp Aiming . . . . . . . . . . . . . . . 350
Bulb Replacement
Bulb Replacement . . . . . . . . . . . . . . . . . . . . . 350
Halogen Bulbs . . . . . . . . . . . . . . . . . . . . . . . . . 350
LED Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
Headlamps, Front Turn Signal, Sidemarker, and Parking Lamps . . . . . . 350
Taillamps, Turn Signal, Stoplamps, and Back-Up Lamps . . . . . . . . . . . . . . . . . . . . . . . 351
Center High-Mounted Stoplamp (CHMSL) and Cargo Lamp . . . . . . . . . . . . 352
License Plate Lamp . . . . . . . . . . . . . . . . . . . . 352
Electrical System
Electrical System Overload . . . . . . . . . . . . . 352
Fuses and Circuit Breakers . . . . . . . . . . . . . 353
Engine Compartment Fuse Block . . . . . . . 353
Instrument Panel Fuse Block (Left) . . . . . 357
Instrument Panel Fuse Block (Right) . . . 358
Wheels and Tires
Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360
All-Season Tires . . . . . . . . . . . . . . . . . . . . . . . . 361
Winter Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
All-Terrain Tires . . . . . . . . . . . . . . . . . . . . . . . 362
Tire Sidewall Labeling . . . . . . . . . . . . . . . . . 362
Tire Designations . . . . . . . . . . . . . . . . . . . . . . 364
Tire Terminology and Definitions . . . . . . 365
Tire Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . 367
Tire Pressure Monitor System . . . . . . . . . 368
Tire Pressure Monitor Operation . . . . . . 369
Tire Inspection . . . . . . . . . . . . . . . . . . . . . . . . . 373
Tire Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . 374
When It Is Time for New Tires . . . . . . . . 375
Buying New Tires . . . . . . . . . . . . . . . . . . . . . 376
Different Size Tires and Wheels . . . . . . . . 377
Uniform Tire Quality Grading . . . . . . . . . . 377
Wheel Alignment and Tire Balance . . . . 378
Wheel Replacement . . . . . . . . . . . . . . . . . . . 378
Tire Chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
If a Tire Goes Flat . . . . . . . . . . . . . . . . . . . . . 380
Tire Changing . . . . . . . . . . . . . . . . . . . . . . . . . . 381
Full-Size Spare Tire . . . . . . . . . . . . . . . . . . . . 390

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 337
Check to see if coolant is visible in the
coolant surge tank. If the coolant inside the
coolant surge tank is boiling, wait until it
cools down. The coolant level should be at
or above the indicated mark. If it is not,
there may be a leak in the cooling system.
If coolant is visible but the coolant level is
not at or above the indicated mark, see the
following sections on how to add coolant to
the coolant surge tank following.
Automatic Coolant Service Fill
Instructions (L3B Engine)
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. Remove the coolant surge tank pressure cap when the cooling system, including
the coolant surge tank pressure cap and
upper radiator hose, is no longer hot.
Turn the pressure cap; slowly
counterclockwise about one full turn. If a
hiss is heard, wait for that to stop.
A hiss means there is still some
pressure left. 2. Keep turning the pressure cap slowly,
and remove it.
3. Fill the coolant surge tank with the proper mixture to the indicated mark.
4. Connect the vehicle to a battery charger.
5. Set the ignition to service mode, see Ignition Positions (Keyless Access) 0230
or
Ignition Positions (Key Access) 0229.
6. Turn off the air conditioning.
7. Set the parking brake.
8. At the same time, press the accelerator and the brake for automatic vehicles for
two seconds, then release.
9. Listen for pump activation and movement of the control valves while
watching the level of the coolant in the
surge tank. Add fluid as the level drops
below the indicated mark on the surge
tank. Allow 15 minutes for the fill and air
removal process to complete.
10. Reinstall the surge tank cap.
If the tank empties, turn the ignition off,
allow the Electronic Control Module (ECM) to
go to sleep, about two minutes, refill to the
indicated mark, and repeat Steps 5–9.
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 warning. The engine could catch
fire and you or others could be burned.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
344 Vehicle Care
Stop/Start System
Vehicles equipped with a 2.7L L3B, 3.0L LM2,
5.3L L84 or 6.2L L87 are equipped with a
Stop/Start system to shut off the engine to
help conserve fuel. SeeStop/Start System
0 233.
Vehicles with the Stop/Start system have an
Absorbed Glass Mat (AGM) 12-volt battery.
Installation of a standard 12-volt battery will
result in reduced 12-volt battery life. When
using a 12-volt battery charger on the 12-volt
AGM battery, some chargers have an AGM
battery setting on the charger. If available,
use the AGM setting on the charger to limit
charge voltage to 14.8 volts. Follow the
charger manufacturer’s instructions.
{Warning
WARNING: Battery posts, terminals, and
related accessories contain lead and lead
compounds, chemicals known to the
State of California to cause cancer and
birth defects or other reproductive harm.
Batteries also contain other chemicals
known to the State of California to cause
cancer. WASH HANDS AFTER HANDLING.
(Continued)
Warning (Continued)
For more information go to
www.P65Warnings.ca.gov/
passenger-vehicle.
See California Proposition 65 Warning 0322
and the back cover.
Vehicle Storage
{Warning
Batteries have acid that can burn you and
gas that can explode. You can be badly
hurt if you are not careful. See Jump
Starting - North America 0391 for tips on
working around a battery without
getting hurt.
Infrequent Usage: Remove the black,
negative (−) cable from the battery to keep
the battery from running down.
Extended Storage: Remove the black,
negative (−) cable from the battery or use a
battery trickle charger.
Negative Battery Cable Disconnection
{Warning
Before disconnecting the negative battery
cable, turn off all features, turn the
ignition off, and remove the key,
if equipped, from the vehicle. If this is
not done, you or others could be injured,
and the vehicle could be damaged.
Caution
If the battery is disconnected with the
ignition on or the vehicle in Retained
Accessory Power (RAP), the OnStar
back-up battery will be permanently
discharged and will need to be replaced.
1. Make sure the lamps, features, and accessories are turned off.
2. Turn the ignition off and remove the key, if equipped.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 347
Starter Switch Check
{Warning
When you are doing this inspection, the
vehicle could move suddenly. If the
vehicle moves, you or others could be
injured.
1. Before starting this check, be sure there is enough room around the vehicle.
2. Apply both the parking brake and the regular brake.
Do not use the accelerator pedal, and be
ready to turn off the engine immediately
if it starts.
3. Try to start the engine in each gear. The vehicle should start only in P (Park) or
N (Neutral). If the vehicle starts in any
other position, contact your dealer for
service.
Automatic Transmission Shift Lock
Control Function Check
{Warning
When you are doing this inspection, the
vehicle could move suddenly. If the
vehicle moves, you or others could be
injured.
1. Before starting this check, be sure there is enough room around the vehicle.
It should be parked on a level surface.
2. Apply the parking brake. Be ready to apply the regular brake immediately if
the vehicle begins to move.
3. With the engine off, turn the ignition on, but do not start the engine. Without
applying the regular brake, try to move
the shift lever out of P (Park) with
normal effort. If the shift lever moves
out of P (Park), contact your dealer for
service.
Ignition Transmission Lock Check
If equipped with Key Access ignition, while
parked, and with the parking brake set, try
to turn the ignition off in each shift lever
position. The ignition should turn to off only
when the shift lever is in P (Park).
The ignition key should come out only when
the ignition is off. Contact your dealer if
service is required.
Park Brake and P (Park)
Mechanism Check
{Warning
When you are doing this check, the
vehicle could begin to move. You or
others could be injured and property
could be damaged. Make sure there is
room in front of the vehicle in case it
begins to roll. Be ready to apply the
regular brake at once should the vehicle
begin to move.
Park on a fairly steep hill, with the vehicle
facing downhill. Keeping your foot on the
regular brake, set the parking brake.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 371
{Warning
Overinflating a tire could cause the tire
to rupture and you or others could be
injured. Do not exceed the maximum
pressure listed on the tire sidewall. See
Tire Sidewall Labeling0362 and
Vehicle Load Limits 0222.
If the tire is overinflated by more than
35 kPa (5 psi), the horn will sound multiple
times and the turn signal lamp will continue
to flash for several seconds after filling
stops. To release and correct the pressure,
while the turn signal lamp is still flashing,
briefly press the center of the valve stem.
When the recommended pressure is reached,
the horn sounds once.
If the turn signal lamp does not flash within
15 seconds after starting to inflate the tire,
the tire fill alert has not been activated or is
not working.
If the hazard warning flashers are on, the
tire fill alert visual feedback will not work
properly. The TPMS will not activate the tire fill alert
properly under the following conditions:.There is interference from an external
device or transmitter.
.The air pressure from the inflation device
is not sufficient to inflate the tire.
.There is a malfunction in the TPMS.
.There is a malfunction in the horn or turn
signal lamps.
.The identification code of the TPMS
sensor is not registered to the system.
.The battery of the TPMS sensor is low.
If the tire fill alert does not operate due to
TPMS interference, move the vehicle about
1 m (3 ft) back or forward and try again.
If the tire fill alert feature is not working,
use a tire pressure gauge.
TPMS Sensor Matching Process
Each TPMS sensor has a unique
identification code. The identification code
needs to be matched to a new tire/wheel
position after rotating the vehicle’s tires or
replacing one or more of the TPMS sensors.
Also, the TPMS sensor matching process
should be performed after replacing a spare
tire with a road tire containing the TPMS
sensor. The malfunction light and the DIC
message should go off at the next ignition cycle. The sensors are matched to the tire/
wheel positions, using a TPMS relearn tool,
in the following order: driver side front tire,
passenger side front tire, passenger side rear
tire, and driver side rear. See your dealer for
service or to purchase a relearn tool.
A TPMS relearn tool can also be purchased.
See Tire Pressure Monitor Sensor Activation
Tool at www.gmtoolsandequipment.com or
call 1-800-GM TOOLS (1-800-468-6657).
There are two minutes to match the first
tire/wheel position, and five minutes overall
to match all four tire/wheel positions. If it
takes longer, the matching process stops
and must be restarted.
The TPMS sensor matching process is:
1. Set the parking brake.
2. Turn the ignition on without starting the vehicle.
3. Uplevel DIC Only: Make sure the Tire Pressure info page option is turned on.
The info pages on the DIC can be turned
on and off through the Options menu.
See Driver Information Center (DIC) (Base
Level) 0124 or
Driver Information Center (DIC) (Midlevel
and Uplevel) 0125.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
396 Vehicle Care
Dinghy Towing (Vehicles with a
Two-Speed Transfer Case)
Only dinghy tow four-wheel-drive vehicles
with a two-speed transfer case that have an
N (Neutral) and a 4
n(Four-Wheel Drive
Low) setting.
{Warning
Shifting a four-wheel-drive vehicle's
transfer case into N (Neutral) can allow
the vehicle to move even if the
transmission is in P (Park). You or others
could be injured. Set the parking brake
and use wheel blocks before shifting the
transfer case to N (Neutral). To dinghy tow:
1. Position the vehicle being towed behind the tow vehicle, facing forward and on a
level surface.
2. Securely attach the vehicle being towed to the tow vehicle.
3. Apply the parking brake and start the engine.
4. Shift the transfer case to N (Neutral). See “Shifting into N (Neutral)” under
Four-Wheel Drive 0242.
5. With the engine running, release the parking brake and verify that the
transfer case is in N (Neutral) by shifting
the transmission to D (Drive) and then to
R (Reverse). There should be no
movement while shifting the
transmission.
6. Shift the transmission to D (Drive).
7. If equipped with an ignition key, turn the ignition to ACC/ACCESSORY.
If equipped with Keyless Access, turn the
engine off. Disregard the Shift to P (Park)
DIC message. See Ignition Positions
(Keyless Access) 0230 or
Ignition Positions (Key Access) 0229.
{Warning
To avoid death, serious injury,
or property damage, before dinghy
towing the vehicle, always disconnect and
secure the negative battery cable and
cover the negative battery post and cable
with a non-conductive material. If the
battery is left connected or the battery
cable contacts the post, the Electric
Parking Brake may activate during
towing, which could cause a crash.
8. Disconnect the negative (–) battery cable. See “Negative Battery Cable
Disconnection” inBattery - North
America 0343.
9. Shift the transmission to P (Park).
Caution
If the steering column is locked, vehicle
damage may occur.
10. Move the steering wheel to make sure the steering column is unlocked.
11. If the vehicle has an ignition key, keep it in the towed vehicle in ACC/ACCESSORY
to prevent the steering column from
locking. If the vehicle is equipped with

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 397
Keyless Access, keep the RKE transmitter
outside of the vehicle and manually lock
the doors. Access the vehicle by using
the key in the door lock. SeeDoor Locks
0 21.
Disconnecting the Towed Vehicle
Before disconnecting from the tow vehicle: 1. Park on a level surface. Secure the vehicle with wheel blocks.
2. Re-connect the negative (–) battery. See Battery - North America 0343.
3. Turn on the ignition with the engine off. For vehicles with a key, turn the ignition
to ON/RUN with the engine off. If the
vehicle is equipped with Keyless Access,
with your foot off the brake pedal, press
and hold ENGINE START/STOP for
five seconds until the green light comes
on in the button. See Ignition Positions
(Keyless Access) 0230 or
Ignition Positions (Key Access) 0229.
4. Set the parking brake. See Electric
Parking Brake 0247.
5. Disconnect from the tow vehicle.
6. Shift the transmission to N (Neutral). 7. Shift the transfer case to 2m(Two-Wheel
Drive High). When the shift to 2
m
(Two-Wheel Drive High) is complete, the
light in the instrument cluster will stop
flashing and stay lit. See
Four-Wheel-Drive Light 0118.
8. Start the engine. Check that the vehicle is in 2
m(Two-Wheel Drive High) by
starting the engine and shifting the
transmission to D (Drive) and then to
R (Reverse). There should be movement
of the vehicle while shifting.
9. Shift the transmission to P (Park) and turn off the ignition.
10. Release the parking brake and remove the wheel blocks.
11. Reset any lost presets. The outside temperature display will
default to 0 °C (32 °F) but will reset with
normal usage.
Dolly Towing