2018 GMC SIERRA wiring

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 335
If TSC is enabled, the Traction
Control System (TCS)/StabiliTrak
warning light will flash on the
instrument cluster. Vehicle speed
must be reduced. If trailer sway
continues, StabiliTrak can reduce
engine torque to help slow the
vehicle. SeeTraction Control/
Electronic Stability Control 0282.
{Warning
Even if the vehicle is equipped
with TSC, trailer sway could result
in loss of control and the vehicle
could crash. If excessive trailer
sway is detected, slow down to a
safe speed. Check the trailer and
vehicle to help correct possible
causes. These could include an
improperly or overloaded trailer,
unrestrained cargo, improper
trailer hitch configuration,
excessive vehicle-trailer speed,
or improperly inflated or incorrect
vehicle or trailer tires. See Towing
Equipment 0325 for trailer
ratings and hitch setup
recommendations. Adding non-dealer accessories can
affect the vehicle performance. See
Accessories and Modifications
0
343.
Electronic Trailer Sway Control
Devices
Some trailers may come equipped
with an electronic device designed
to reduce or control trailer sway.
Aftermarket equipment
manufacturers also offer similar
devices that connect to the wiring
between the trailer and the vehicle.
These devices may interfere with
the vehicle’ s trailer brake or other
systems, including integrated
anti-sway systems, if equipped.
Messages related to trailer
connections or trailer brakes could
appear on the Driver Information
Center (DIC). The effect that these
devices may have on vehicle
handling or trailer brake
performance is unknown.
{Warning
Use of electronic trailer sway
control devices could result in
reduced trailer brake
performance, loss of trailer
brakes, or other malfunctions, and
could cause a crash. You or
others could be injured or killed.
Before using one of these
devices:
. Ask the device or trailer
manufacturer if the device
has been thoroughly tested
for compatibility with the
make, model, and year of
the vehicle as well as
optional equipment installed
on the vehicle.
. Before driving on the open
roads, check that the trailer
brakes are working properly.
Drive the vehicle with the
trailer attached on a level
road surface that is free of
traffic at about 32-40 km/h
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
336 Driving and Operating
Warning (Continued)
(20-25 mph) and fully apply
the manual trailer brake
apply lever. Also check that
the trailer brake lamps and
other lamps are functioning
correctly.
. If the trailer brakes are not
operating properly at any
time, or if a DIC message
indicates problems with the
trailer connections or trailer
brakes, carefully pull the
vehicle over to the side of
the road when traffic
conditions allow.
Conversions and
Add-Ons
Add-On Electrical
Equipment
{Warning
The Data Link Connector (DLC) is
used for vehicle service
and Emission Inspection/
Maintenance testing. See
Malfunction Indicator Lamp
(Check Engine Light) 0150.
A device connected to the DLC —
such as an aftermarket fleet or
driver-behavior tracking device —
may interfere with vehicle
systems. This could affect vehicle
operation and cause a crash.
Such devices may also access
information stored in the vehicle’s
systems.
Caution
Some electrical equipment can
damage the vehicle or cause
components to not work and
would not be covered by the
vehicle warranty. Always check
with your dealer before adding
electrical equipment.
Add-on equipment can drain the
vehicle's 12-volt battery, even if the
vehicle is not operating.
The vehicle has an airbag system.
Before attempting to add anything
electrical to the vehicle, see
Servicing the Airbag-Equipped
Vehicle 090 and Adding Equipment
to the Airbag-Equipped Vehicle
0 90.
For information on wiring auxiliary
switches, see www.gmupfitter.com
or contact your dealer.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
340 Driving and Operating
go to a weigh station and weigh the
vehicle. Your dealer can also help
with this.
The total vehicle reserve capacity
for the vehicle is in the lower right
corner of the Certification/Tire label
as shown previously.
See your dealer for additional
advice and information about using
a snow plow on the vehicle. Also,
seeVehicle Load Limits 0248.
Emergency Roof Lamp
Provisions
Vehicles with the RPO VYU snow
plow prep package also have an
emergency roof lamp provision
package, RPO TRW. Wiring for the
emergency roof lamp is provided
above the overhead console. See
Auxiliary Roof-Mounted Lamp 0182
for switch location.
Pickup Conversion to
Chassis Cab
We are aware that some vehicle
owners might consider having the
pickup box removed and a
commercial or recreational body
installed. Owners should be aware
that, as manufactured, there are
differences between a chassis cab
and a pickup with the box removed
which could affect vehicle safety.
The components necessary to adapt
a pickup to permit its safe use with
a specialized body should be
installed by the body builder.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Vehicle Care 341
Vehicle Care
General Information
General Information . . . . . . . . . . 342
California Proposition65 Warning . . . . . . . . . . . . . . . . . 343
California Perchlorate Materials Requirements . . . . . 343
Accessories and Modifications . . . . . . . . . . . . . . . . 343
Vehicle Checks
Doing Your OwnService Work . . . . . . . . . . . . . . . 344
Hood . . . . . . . . . . . . . . . . . . . . . . . . . 344
Engine Compartment Overview . . . . . . . . . . . . . . . . . . . . 345
Engine Oil . . . . . . . . . . . . . . . . . . . . 350
Engine Oil Life System . . . . . . . 353
Automatic Transmission Fluid (6-Speed Transmission) . . . . . 354
Automatic Transmission Fluid (8-Speed Transmission) . . . . . 357
Engine Air Cleaner/Filter . . . . . . 358
Cooling System . . . . . . . . . . . . . . 359
Engine Overheating . . . . . . . . . . 363
Overheated Engine Protection Operating Mode . . . . . . . . . . . . . 364
Engine Fan . . . . . . . . . . . . . . . . . . . 365 Power Steering Fluid (1500
Series) . . . . . . . . . . . . . . . . . . . . . . 365
Power Steering Fluid (2500/ 3500 Series) . . . . . . . . . . . . . . . . 365
Washer Fluid . . . . . . . . . . . . . . . . . 366
Brakes . . . . . . . . . . . . . . . . . . . . . . . 367
Brake Fluid . . . . . . . . . . . . . . . . . . . 368
Battery - North America . . . . . . 369
Four-Wheel Drive . . . . . . . . . . . . . 370
Front Axle . . . . . . . . . . . . . . . . . . . . 370
Rear Axle . . . . . . . . . . . . . . . . . . . . 371
Noise Control System . . . . . . . . 373
Starter Switch Check . . . . . . . . . 374
Automatic Transmission Shift
Lock Control Function
Check . . . . . . . . . . . . . . . . . . . . . . . 374
Ignition Transmission Lock Check . . . . . . . . . . . . . . . . . . . . . . . 374
Park Brake and P (Park) Mechanism Check . . . . . . . . . . 375
Wiper Blade Replacement . . . . 375
Windshield Replacement . . . . . 376
Gas Strut(s) . . . . . . . . . . . . . . . . . . 376
Headlamp Aiming
Headlamp Aiming . . . . . . . . . . . . 377
Bulb Replacement
Bulb Replacement . . . . . . . . . . . . 378
Halogen Bulbs . . . . . . . . . . . . . . . . 378 High Intensity Discharge (HID)
Lighting . . . . . . . . . . . . . . . . . . . . . 378
LED Lighting . . . . . . . . . . . . . . . . . 378
Taillamps, Turn Signal, Stoplamps, and Back-Up
Lamps . . . . . . . . . . . . . . . . . . . . . . 378
Center High-Mounted Stoplamp (CHMSL) and
Cargo Lamp . . . . . . . . . . . . . . . . . 380
Electrical System
High Voltage Devices andWiring . . . . . . . . . . . . . . . . . . . . . . . 380
Electrical System Overload . . . 380
Fuses and Circuit Breakers . . . 381
Engine Compartment Fuse Block . . . . . . . . . . . . . . . . . . . . . . . . 381
Instrument Panel Fuse Block (Right) . . . . . . . . . . . . . . . . . . . . . . 385
Instrument Panel Fuse Block (Left) . . . . . . . . . . . . . . . . . 386
Wheels and Tires
Tires . . . . . . . . . . . . . . . . . . . . . . . . . . 389
All-Season Tires . . . . . . . . . . . . . . 389
Winter Tires . . . . . . . . . . . . . . . . . . 390
Low-Profile Tires . . . . . . . . . . . . . 390
All-Terrain Tires . . . . . . . . . . . . . . . 391
Tire Sidewall Labeling . . . . . . . . 391
Tire Designations . . . . . . . . . . . . . 393

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
380 Vehicle Care
Center High-Mounted
Stoplamp (CHMSL) and
Cargo Lamp
1. Cargo Lamp Bulbs
2. Center High-MountedStoplamp (CHMSL) Bulb
To replace one of these bulbs:
1. Remove the two screws and lift off the lamp assembly.
2. Turn the bulb socket counterclockwise and pull it
straight out.
3. Pull the bulb straight out from the socket.
Electrical System
High Voltage Devices and
Wiring
For an eAssist vehicle, see the
Silverado/Sierra eAssist
supplement.
Electrical System
Overload
The vehicle has fuses to protect
against an electrical system
overload. Fuses also protect power
devices in the vehicle.
Replace a bad fuse with a new one
of the identical size and rating.
If there is a problem on the road and
a fuse needs to be replaced, there
are some spare fuses and a fuse
puller in the left instrument panel
fuse block. The same amperage
fuse can also be borrowed. Choose
some feature of the vehicle that is
not needed to use and replace it as
soon as possible.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Vehicle Care 381
Headlamp Wiring
An electrical overload may cause
the lamps to go on and off, or in
some cases to remain off. Have the
headlamp wiring checked right away
if the lamps go on and off or
remain off.
Windshield Wipers
If the wiper motor overheats due to
heavy snow or ice, the windshield
wipers will stop until the motor cools
and will then restart.
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 the
windshield wipers.
If the overload is caused by an
electrical problem and not snow or
ice, be sure to get it fixed.
Fuses and Circuit
Breakers
The wiring circuits in the vehicle are
protected from short circuits by a
combination of fuses and circuit
breakers. This greatly reduces the
chance of damage caused by
electrical problems.
{Danger
Fuses and circuit breakers are
marked with their ampere rating.
Do not exceed the
specified amperage rating when
replacing fuses and circuit
breakers. Use of an oversized
fuse or circuit breaker can result
in a vehicle fire. You and others
could be seriously injured or
killed.
To check a fuse, look at the
silver-colored band inside the fuse.
If the band is broken or melted,
replace the fuse. Be sure to replace
a bad fuse with a new one of the
identical size and rating. Fuses of the same amperage can
be temporarily borrowed from
another fuse location, if a fuse goes
out. Replace the fuse as soon as
possible.
Engine Compartment
Fuse Block
If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
The engine compartment fuse block
is in the engine compartment, on
the driver side of the vehicle.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
496 Index
General Information (cont'd)Vehicle Care . . . . . . . . . . . . . . . . . . 342
Glove Box . . . . . . . . . . . . . . . . . . . . . . 124
GM Mobility Reimbursement Program . . . . . . . . . . . . . . . . . . . . . . . 469
H
Halogen Bulbs . . . . . . . . . . . . . . . . . . 378
Hazard Warning Flashers . . . . . . . 180
Head Restraints . . . . . . . . . . . . . . . . . 58
HeadlampsAiming . . . . . . . . . . . . . . . . . . . . . . . . 377
Automatic . . . . . . . . . . . . . . . . . . . . . 179
Bulb Replacement . . . . . . . . . . . . 378
Daytime RunningLamps (DRL) . . . . . . . . . . . . . . . . 179
Flash-to-Pass . . . . . . . . . . . . . . . . . 179
High Intensity Discharge (HID) Lighting . . . . . . . . . . . . . . . 378
High-Beam On Light . . . . . . . . . . 157
High/Low Beam Changer . . . . . 179
Lamps On Reminder . . . . . . . . . 157
Heated Steering Wheel . . . . . . . . . . . . . . . 130
Heated and Ventilated Front Seats . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Heated Mirrors . . . . . . . . . . . . . . . . . . . 50 Heater
Engine Coolant . . . . . . . . . . . . . . . 260
Heating . . . . . . . . . . . . . . .224, 226, 228
High Voltage Devices and Wiring . . . . . . . . . . . . . . . . . . . . . . . . . 380
High-Beam On Light . . . . . . . . . . . . 157
High-Speed Operation . . . . . . . . . . 399
Hill and Mountain Roads . . . . . . . . 245
Hill Descent Control (HDC) . . . . . 284
Hill Descent Control Light . . . . . . . 153
Hill Start Assist (HSA) . . . . . . . . . . 282
Home Page . . . . . . . . . . . . . . . . . . . . . 189
Hood . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
Horn . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
How to Wear Seat Belts Properly . . . . . . . . . . . . . . . . . . . . . . . . 70
HVAC . . . . . . . . . . . . . . . . .224, 226, 228
I
Idle System Fast . . . . . . . . . . . . . . . . . . . . . . . . . . 259
Ignition Positions . . . . . . . . . . . . . . . 256
Ignition Transmission Lock Check . . . . . . . . . . . . . . . . . . . . . . . . . 374
Immobilizer . . . . . . . . . . . . . . . . . . . . . . 46
Indicator Vehicle Ahead . . . . . . . . . . . . . . . . 154 Infants and Young Children,
Restraints . . . . . . . . . . . . . . . . . . . . . . 94
Infotainment . . . . . . . . . . . . . . . . . . . . 186
Infotainment System . . . . . . . . . . . . 478
Instrument Cluster . . . . . . . . . . . . . . 138
Instrument Panel Storage Area . . . . . . . . . . . . . . . . . 124
Interior Rearview Mirrors . . . . . . . . . 51
Introduction . . . . . . . . . . . . . . . . . . . . . . . 2
J
Jack Auxiliary . . . . . . . . . . . . . . . . . . . . . . 203
Jump Starting - North America . . . . . . . . . . . . . . . . . . . . . . . 426
K
Keyless EntryRemote (RKE) System . . . . . . . . . 37
Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
L
Labeling, Tire Sidewall . . . . . . . . . . 391
Lamps Auxiliary RoofMounted Lamp . . . . . . . . . . . . . . 182
Cargo . . . . . . . . . . . . . . . . . . . . . . . . . 183
Daytime Running (DRL) . . . . . . 179
Dome . . . . . . . . . . . . . . . . . . . . . . . . . 183

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
502 Index
Towing (cont'd)Trailer . . . . . . . . . . . . . . . . . . . . . . . . 307
Trailer Sway Control (TSC) . . . 334
Vehicle . . . . . . . . . . . . . . . . . . . . . . . 430
Traction Control System (TCS)/StabiliTrak Light . . . . . . . . . . . . . 155
Off Light . . . . . . . . . . . . . . . . . . . . . . 154
Traction Control/Electronic
Stability Control . . . . . . . . . . . . . . . 282
Trademarks and License Agreements . . . . . . . . . . . . . . . . . . . 218
Trailer Sway Control (TSC) . . . . . . . . . . 334
Tow Mirrors . . . . . . . . . . . . . . . . . . . . . 48
Towing . . . . . . . . . . . . . . . . . . . . . . . . 307
Transfer Case . . . . . . . . . . . . . . . . . . 272
Transmission Automatic . . . . . . . . . . . . . . . . . . . . . 265
Fluid, Automatic . . . . . . . . . 354, 357
Temperature Gauge . . . . . . . . . . 145
Transportation Program, Courtesy . . . . . . . . . . . . . . . . . . . . . . 471
Trip Odometer . . . . . . . . . . . . . . . . . . 142
Truck-Camper Loading Information . . . . . . . . . . . . . . . . . . . . 253
Turn and Lane-Change Signals . . . . . . . . . . . . . . . . . . . . . . . . 181 Turn Signal
Bulb Replacement . . . . . . . . . . . . 378
U
Uniform Tire Quality Grading . . . 410
Universal Remote System . . . . . . 172Operation . . . . . . . . . . . . . . . . . . . . . 174
Programming . . . . . . . . . . . . . . . . . 172
Updates Software . . . . . . . . . . . . . . . . . . . . . . 189
USB Port . . . . . . . . . . . . . . . . . . . . . . . 197
Using This Manual . . . . . . . . . . . . . . . . 2
V
Vehicle Alarm System . . . . . . . . . . . . . . . . . . 44
Canadian Owners . . . . . . . . . . . . . . . 2
Control . . . . . . . . . . . . . . . . . . . . . . . 236
Identification Number (VIN) . . . 460
Load Limits . . . . . . . . . . . . . . . . . . . 248
Messages . . . . . . . . . . . . . . . . . . . . 164
Personalization . . . . . . . . . . . . . . . 165
Remote Start . . . . . . . . . . . . . . . . . . . 39
Security . . . . . . . . . . . . . . . . . . . . . . . . 44
Speed Messages . . . . . . . . . . . . . 164
Towing . . . . . . . . . . . . . . . . . . . . . . . . 430
Vehicle Ahead Indicator . . . . . . . . 154 Vehicle Care
Tire Pressure . . . . . . . . . . . . . . . . . 397
Vehicle Data Recording and Privacy . . . . . . . . . . . . . . . . . . . . . . . . 477
Ventilation, Air . . . . . . . . . . . . . . . . . . 231
Visors . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Voice Recognition . . . . . . . . . . . . . . 205
Voltage Devices and Wiring . . . . 380
Voltmeter Gauge . . . . . . . . . . . . . . . 145
W
Warning Brake System Light . . . . . . . . . . . 152
Caution and Danger . . . . . . . . . . . . . 3
Lane Departure (LDW) . . . . . . . 295
Warning Lights, Gauges, and Indicators . . . . . . . . . . . . . . . . . . . . . 137
Warnings Hazard Flashers . . . . . . . . . . . . . . 180
Washer Fluid . . . . . . . . . . . . . . . . . . . 366
Wheels Alignment and Tire Balance . . .411
Different Size . . . . . . . . . . . . . . . . . 409
Replacement . . . . . . . . . . . . . . . . . 412
When It Is Time for New Tires . . . . . . . . . . . . . . . . . . . . . . . . . . 407
Where to Put the Restraint . . . . . . 98
Wi-Fi . . . . . . . . . . . . . . . . . . . . . . . . . . . 482