2021 CHEVROLET SILVERADO 2500HD check engine

Chevrolet Silverado 2500 HD/3500 HD Owner Manual (GMNA-Localizing-U.
S./Canada/Mexico-14632154) - 2021 - CRC - 11/20/20
Service and Maintenance 389
Maintenance Schedule Additional
Required Services - Severe12 000 km/7,500 mi
24 000 km/15,000 mi
36 000 km/22,500 mi
48 000 km/30,000 mi 60 000 km/37,500 mi
72 000 km/45,000 mi84 000 km/52,500 mi
96 000 km/60,000 mi
108 000 km/67,500 mi 120 000 km/75,000 mi 132 000 km/82,500 mi
144 000 km/90,000 mi 156 000 km/97,500 mi
168 000 km/105,000 mi 180 000 km/112,500 mi
192 000 km/120,000 mi 204 000 km/127,500 mi 216 000 km/135,000 mi
228 000 km/142,500 mi
240 000 km/150,000 mi
Rotate tires and perform Required Services. Check engine oil
level and oil life percentage. Change engine oil and filter,
if needed.
Check engine air filter life percentage and status. Change
engine air filter, if needed. (1)
@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
Replace passenger compartment air filter. (2)@ @@@@@
Inspect evaporative control system. (3)@ @@
Replace spark plugs. Inspect spark plug wires and/or boots.@
Change automatic transmission fluid and filter.@@@
Change transfer case fluid, if equipped with 4WD. (4)@@@@@@
Drain and fill engine cooling system. (5)@
Visually inspect accessory drive belts. (6)@
Replace brake fluid. (7)
Replace windshield wiper blades. (8)
@ @ @ @ @ @ @ @ @ @
Replace hood gas struts and tailgate dampener. (9)@ @
Replace air conditioning desiccant. (10)

Chevrolet Silverado 2500 HD/3500 HD Owner Manual (GMNA-Localizing-U.
S./Canada/Mexico-14632154) - 2021 - CRC - 11/20/20
390 Service and Maintenance
Footnotes—Maintenance Schedule
Additional Required Services - Severe
(1) Or every four years, whichever comes
first. If driving in dusty conditions, inspect
the filter at each oil change or more often
as needed. See Engine Air Cleaner/Filter
0 309.
(2) Or every two years, whichever comes
first. More frequent replacement may be
needed if the vehicle is driven in areas with
heavy traffic, poor air quality, areas with
high dust levels or are sensitive to
environmental allergens. Filter replacement
may also be needed if you notice reduced
airflow, windows fogging up, or odors. Your
local GM Service location can help you
determine when it is the right time to
replace your filter.
(3) Visually check all fuel and vapor lines
and hoses for proper attachment,
connection, routing, and condition.
(4) Do not directly power wash the transfer
case and/or front/rear axle output seals.
High pressure water can overcome the seals
and contaminate the fluid. Contaminated
fluid will decrease the life of the transfer
case and/or drive axles and should be
replaced. (5)
Or every five years, whichever comes
first. See Cooling System 0310.
(6) Or every 10 years, whichever comes first.
Inspect for fraying, excessive cracking,
or damage; replace, if needed.
(7) Replace brake fluid every five years. See
Brake Fluid 0317.
(8) Or every 12 months, whichever comes
first. See Wiper Blade Replacement 0322.
(9) Or every 10 years, whichever comes first.
See Gas Strut(s) 0323.
(10) Replace air conditioning desiccant every
seven years.
Special Application Services
.Vehicles with Dual Wheels: Check dual
wheel nut torque at 160, 1 600, and
10 000 km (100, 1,000, and 6,000 mi) of
driving. Repeat this service whenever a
tire/wheel is serviced or removed.
.Severe Commercial Use Vehicles Only:
Lubricate chassis components every oil
change.
.Have underbody flushing service
performed. See “Underbody Maintenance”
in Exterior Care 0373.
Additional Maintenance
and Care
Your vehicle is an important investment and
caring for it properly may help to avoid
future costly repairs. To maintain vehicle
performance, additional maintenance
services may be required.
It is recommended that your dealer perform
these services —their trained dealer
technicians know your vehicle best. Your
dealer can also perform a thorough
assessment with a multi-point inspection to
recommend when your vehicle may need
attention.
The following list is intended to explain the
services and conditions to look for that may
indicate services are required.
Battery
The 12-volt battery supplies power to start
the engine and operate any additional
electrical accessories.
.To avoid break-down or failure to start
the vehicle, maintain a battery with full
cranking power.

Chevrolet Silverado 2500 HD/3500 HD Owner Manual (GMNA-Localizing-U.
S./Canada/Mexico-14632154) - 2021 - CRC - 11/20/20
Service and Maintenance 391
.Trained dealer technicians have the
diagnostic equipment to test the battery
and ensure that the connections and
cables are corrosion-free.
Belts
.Belts may need replacing if they squeak
or show signs of cracking or splitting.
.Trained dealer technicians have access to
tools and equipment to inspect the belts
and recommend adjustment or
replacement when necessary.
Brakes
Brakes stop the vehicle and are crucial to
safe driving.
.Signs of brake wear may include chirping,
grinding, or squealing noises, or difficulty
stopping.
.Trained dealer technicians have access to
tools and equipment to inspect the brakes
and recommend quality parts engineered
for the vehicle. Fluids
Proper fluid levels and approved fluids
protect the vehicle’s systems and
components. See
Recommended Fluids and
Lubricants 0393 for GM approved fluids.
.Engine oil and windshield washer fluid
levels should be checked at every fuel fill.
.Instrument cluster lights may come on to
indicate that fluids may be low and need
to be filled.
Hoses
Hoses transport fluids and should be
regularly inspected to ensure that there are
no cracks or leaks. With a multi-point
inspection, your dealer can inspect the hoses
and advise if replacement is needed.
Lamps
Properly working headlamps, taillamps, and
brake lamps are important to see and be
seen on the road.
.Signs that the headlamps need attention
include dimming, failure to light, cracking,
or damage. The brake lamps need to be
checked periodically to ensure that they
light when braking.
.With a multi-point inspection, your dealer
can check the lamps and note any
concerns.
Shocks and Struts
Shocks and struts help aid in control for a
smoother ride.
.Signs of wear may include steering wheel
vibration, bounce/sway while braking,
longer stopping distance, or uneven
tire wear.
.As part of the multi-point inspection,
trained dealer technicians can visually
inspect the shocks and struts for signs of
leaking, blown seals, or damage, and can
advise when service is needed.
Tires
Tires need to be properly inflated, rotated,
and balanced. Maintaining the tires can save
money and fuel, and can reduce the risk of
tire failure.
.Signs that the tires need to be replaced
include three or more visible treadwear
indicators; cord or fabric showing through
the rubber; cracks or cuts in the tread or
sidewall; or a bulge or split in the tire.

Chevrolet Silverado 2500 HD/3500 HD Owner Manual (GMNA-Localizing-U.
S./Canada/Mexico-14632154) - 2021 - CRC - 11/20/20
Technical Data 399
ApplicationCapacities
Metric English
I3500 Series Chassis Cab –Front Tank 89.0 L
23.5 gal
I3500 Series Chassis Cab –Rear Tank 151.4 L
40.0 gal
Transfer Case Fluid 2.3 L2.4 qt
Hydraulic Power Steering Fluid 2.0 L2.1 qt
Wheel Nut Torque 190Y 140 lb ft
All capacities are approximate. When adding, be sure to fill to the approximate level, as recommended in this manual. Recheck fluid level
after filling.
*Engine cooling system capacity values are based on the entire cooling system and its components.
Engine Specifications
Engine VIN CodeSpark Plug Gap
6.6L V8 (L8T) 70.95–1.10 mm (0.037–0.043 in)
Spark plug gaps are preset by the manufacturer. Re-gapping the spark plug is not recommended and can damage the spark plug.

Chevrolet Silverado 2500 HD/3500 HD Owner Manual (GMNA-Localizing-U.
S./Canada/Mexico-14632154) - 2021 - CRC - 11/20/20
OnStar 413
.Receive a Diagnostic check of the vehicle's
key operating systems.
.Receive Roadside Assistance.
.Manage Wi-Fi Settings, if equipped.
Press
>to get a priority connection to an
OnStar Advisor available 24/7 to:
.Get help for an emergency.
.Be a Good Samaritan or respond to an
AMBER Alert.
.Get assistance in severe weather or other
crisis situations and find evacuation
routes.
OnStar Services
Emergency
Emergency Services require an active safety
and security plan. With Automatic Crash
Response, built-in sensors can automatically
alert a specially trained OnStar Advisor who
is immediately connected in to the vehicle
to help.
Press
>for a priority connection to an
OnStar Advisor who can contact emergency
service providers, direct them to your exact
location, and relay important information. With OnStar Crisis Assist, specially trained
Advisors are available 24 hours a day, 7 days
a week, to provide a central point of
contact, assistance, and information during a
crisis.
With Roadside Assistance, Advisors can
locate a nearby service provider to help with
a flat tire, a battery jump, or an empty
gas tank.
Security
If equipped, OnStar provides these services:
.With Stolen Vehicle Assistance, OnStar
Advisors can use GPS to pinpoint the
vehicle and help authorities quickly
recover it.
.With Remote Ignition Block, if equipped,
OnStar can block the engine from being
restarted.
.With Stolen Vehicle Slowdown,
if equipped, OnStar can work with law
enforcement to gradually slow the
vehicle down.
Theft Alarm Notification
If equipped, if the doors are locked and the
vehicle alarm sounds, a notification by text,
e-mail, or phone call will be sent. If the
vehicle is stolen, an OnStar Advisor can work
with authorities to recover the vehicle.
OnStar Additional
Information
In-Vehicle Audio Messages
Audio messages may play important
information at the following times:
.Prior to vehicle purchase. PressQto
set up an account.
.After change in ownership and at
90 days.
Transferring Service
PressQto request account transfer
eligibility information. The Advisor can
cancel or change account information.
Selling/Transferring the Vehicle
Call 1-888-4ONSTAR (1-888-466-7827)
immediately to terminate your OnStar or
connected services if the vehicle is disposed
of, sold, transferred, or if the lease ends.

Chevrolet Silverado 2500 HD/3500 HD Owner Manual (GMNA-Localizing-U.
S./Canada/Mexico-14632154) - 2021 - CRC - 11/20/20
420 Index
IndexA
Accessories and Modifications . . . . . . . . . . . 302
Accessory Power . . . . . . . . . . . . . . . . . . . . . . . . . 229
Add-On Electrical Equipment . . . . . . . . . . . . . 297
Adding a Snow Plow or SimilarEquipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
Additional Information OnStar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413
Additional Maintenance and Care . . . . . . . . 390
Adjustments Lumbar, Front Seats . . . . . . . . . . . . . . . . . . . . 45
Agreements Trademarks and License . . . . . . . . . . . . . . . 190
Air Cleaner/Filter, Engine . . . . . . . . . . . . . . . . 309
Air Conditioning . . . . . . . . . . . . . . . . . . . . .199, 201
Air Filter
Life System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
Air Filter, Passenger Compartment . . . . . . . 204
Air Vents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Airbag System Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
How Does an Airbag Restrain? . . . . . . . . . . 61
Passenger Sensing System . . . . . . . . . . . . . . 62
What Makes an Airbag Inflate? . . . . . . . . . 61
What Will You See after an AirbagInflates? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
When Should an Airbag Inflate? . . . . . . . . 60
Where Are the Airbags? . . . . . . . . . . . . . . . . 59 Airbags
Adding Equipment to the Vehicle . . . . . . . 66
Passenger Status Indicator . . . . . . . . . . . . . 110
Readiness Light . . . . . . . . . . . . . . . . . . . . . . . . 110
Servicing Airbag-Equipped Vehicles . . . . . . 66
System Check . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Alarm
Vehicle Security . . . . . . . . . . . . . . . . . . . . . . . . 27
Alert Lane Change . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
Side Blind Zone (SBZA) . . . . . . . . . . . . . . . . . 260
All-Season Tires . . . . . . . . . . . . . . . . . . . . . . . . . . 337
All-Terrain Tires . . . . . . . . . . . . . . . . . . . . . . . . . . 337
AM-FM Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Antenna Fixed Mast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Multi-band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Antilock Brake System (ABS) . . . . . . . . . . . . . 240 Warning Light . . . . . . . . . . . . . . . . . . . . . . . . . . 114
Appearance Care Exterior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
Interior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378
Apple CarPlay and Android Auto . . . . . . . . . 180
Assistance Program, Roadside . . . . . . . . . . . . 404
Assistance Systems for Driving . . . . . . . . . . 257
Assistance Systems for Parking and Backing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

Chevrolet Silverado 2500 HD/3500 HD Owner Manual (GMNA-Localizing-U.
S./Canada/Mexico-14632154) - 2021 - CRC - 11/20/20
Index 421
AudioBluetooth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Automatic Dimming Mirrors . . . . . . . . . . . . . . . . . . . . . . . 33
Door Locks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Emergency Braking (AEB) . . . . . . . . . . . . . . 259
Headlamp System . . . . . . . . . . . . . . . . . . . . . 136
Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
Transmission Fluid . . . . . . . . . . . . . . . . . . . . . 308
Automatic Transmission Manual Mode . . . . . . . . . . . . . . . . . . . . . . . . . 235
Shift Lock Control Function Check . . . . . . 322
Auxiliary Roof Mounted Lamp . . . . . . . . . . . . . . . . . . . 139
Auxiliary Jack . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
Avoiding Untrusted Media Devices . . . . . . . . 153
Axle, Front . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
Axle, Rear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
B
Battery Exterior Lighting Battery Saver . . . . . . . . 142
Load Management . . . . . . . . . . . . . . . . . . . . . . 141
Power Protection . . . . . . . . . . . . . . . . . . . . . . 142
Battery - North America . . . . . . . . . . . . .318, 367
Blade Replacement, Wiper . . . . . . . . . . . . . . . 322
Blind Spot Mirrors . . . . . . . . . . . . . . . . . . . . . . . . .33 Bluetooth
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 175, 176
Bluetooth Audio . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Brake Parking, Electric . . . . . . . . . . . . . . . . . . . . . . . . 240
System Warning Light . . . . . . . . . . . . . . . . . . 113
Brake Pad Life System . . . . . . . . . . . . . . . . . . . 316
Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
Antilock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
Assist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
Pad Life System . . . . . . . . . . . . . . . . . . . . . . . 316
Braking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 Automatic Emergency (AEB) . . . . . . . . . . . 259
Break-In, New Vehicle . . . . . . . . . . . . . . . . . . . . 223
Bulb Replacement Center High-Mounted Stoplamp(CHMSL) and Cargo Lamp . . . . . . . . . . . . 327
Halogen Bulbs . . . . . . . . . . . . . . . . . . . . . . . . . 325
Headlamp Aiming . . . . . . . . . . . . . . . . . . . . . . 324
Headlamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
Headlamps, Front Turn Signal, Sidemarker, and Parking Lamps . . . . . . 325
License Plate Lamps . . . . . . . . . . . . . . . . . . . 328
Taillamps, Turn Signal, Stoplamps, and Back-up Lamps . . . . . . . . . . . . . . . . . . 326
Buying New Tires . . . . . . . . . . . . . . . . . . . . . . . . . 351
C
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
California Perchlorate Materials Requirements . . . 301
California Proposition
65 Warning . . . . . . . . . . . . . . . . . . .301, 318, 367, Back Cover
Camera Truck Bed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Canadian Vehicle Owners . . . . . . . . . . . . . . . . . . . 1
Capacities and Specifications . . . . . . . . . . . . . 398
Carbon Monoxide
Engine Exhaust . . . . . . . . . . . . . . . . . . . . . . . . 232
Tailgate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Winter Driving . . . . . . . . . . . . . . . . . . . . . . . . . 215
Cargo Tie-Downs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Caution, Danger, and Warning . . . . . . . . . . . . . .2
Center Console Storage . . . . . . . . . . . . . . . . . . . 92
Center High-Mounted Stoplamp (CHMSL) and Cargo Lamp . . . . . . . . . . . . . . 327
Center Seat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Chains, Tire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
Charging Wireless . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Charging System Light . . . . . . . . . . . . . . . . . . . . 111
Check Engine Light (Malfunction Indicator) . . . . 111

Chevrolet Silverado 2500 HD/3500 HD Owner Manual (GMNA-Localizing-U.
S./Canada/Mexico-14632154) - 2021 - CRC - 11/20/20
422 Index
Check (cont'd)Ignition Transmission Lock . . . . . . . . . . . . . 322
Child Restraints Infants and Young Children . . . . . . . . . . . . . 69
Lower Anchors and Tethers forChildren . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Older Children . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Securing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84, 87
Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Circuit Breakers . . . . . . . . . . . . . . . . . . . . . . . . . . 329
Cleaning Exterior Care . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
Interior Care . . . . . . . . . . . . . . . . . . . . . . . . . . . 378
Climate Control Systems . . . . . . . . . . . . . . . . . 199 Air Conditioning . . . . . . . . . . . . . . . . . . . . . . . 199
Dual Automatic . . . . . . . . . . . . . . . . . . . . . . . . 201
Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Cluster, Instrument . . . . . . . . . . . . . . . . . . . . . . 102
Collision Damage Repair . . . . . . . . . . . . . . . . . 407
Compartments Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Compass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Connected Services Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . 418
Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419
Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417 Connections
Connected Services . . . . . . . . . . . . . . . . . . . . 418
Control Hill Descent . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
Traction and Electronic Stability . . . . . . . 242
Control Light Hill Descent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
Control of a Vehicle . . . . . . . . . . . . . . . . . . . . . 208
Controls Steering Wheel . . . . . . . . . . . . . . . . . . . . . . . . 146
Convex Mirrors . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Coolant
Engine Temperature Gauge . . . . . . . . . . . . 108
Engine Temperature Warning Light . . . . . 116
Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199, 201
Cooling System . . . . . . . . . . . . . . . . . . . . . . . . . . 310
Courtesy Transportation Program . . . . . . . . 406
Coverage Explanations . . . . . . . . . . . . . . . . . . . 170
Cruise Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Cupholders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91
Customer Assistance . . . . . . . . . . . . . . . . . . . . . 403
Offices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403
Text Telephone (TTY) Users . . . . . . . . . . . . 403
Customer Information
Publications Ordering Information . . . . . 408
Customer Satisfaction Procedure . . . . . . . . . 401
Cybersecurity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410D
Damage Repair, Collision . . . . . . . . . . . . . . . . . 407
Danger, Warning, and Caution . . . . . . . . . . . . . .2
Data Collection Infotainment System . . . . . . . . . . . . . . . . . . . 411
OnStar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411
Data Recorders, Event . . . . . . . . . . . . . . . . . . . . 411
Database Coverage Explanations . . . . . . . . . 170
Daytime Running Lamps (DRL) . . . . . . . . . . . 136
Defensive Driving . . . . . . . . . . . . . . . . . . . . . . . . 208
Delayed Locking . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Destination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
Diagnostics Connected Services . . . . . . . . . . . . . . . . . . . . 419
Differential, Limited-Slip . . . . . . . . . . . . . . . . . 245
Distracted Driving . . . . . . . . . . . . . . . . . . . . . . . . 207
Dome Lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Door Ajar Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Delayed Locking . . . . . . . . . . . . . . . . . . . . . . . . 22
Locks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Power Locks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Drive Belt Routing, Engine . . . . . . . . . . . . . . .400
Driver Teen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
Driver Assistance Systems . . . . . . . . . . . . . . . 247
Driver Information Center (DIC) . . . . . . 119, 120
Driver Mode Control . . . . . . . . . . . . . . . . . . . . . 244