Dashboard Symbols: 2021 GMC Sierra HD Warning Lights Guide
The 2021 GMC Sierra HD’s dashboard icons and warning lights are called critical indicators. They tell drivers important things about the car’s state and possible problems. These lights flash to let drivers know about a number of problems, such as low fuel, engine problems, uneven tire pressure, and upcoming repairs. It’s important to understand these symbols so that you can act quickly and correctly to keep the car safe and running at its best. The simple look and useful information of the dashboard symbols help drivers stay alert and responsive on the road, which encourages them to take an active role in safety and car maintenance.
2023 GMC SIERRA 1500 Specs, Price, Features, and Mileage (Brochure)
Seat Belt Reminders
Driver Seat Belt Reminder Light
There is a driver seat belt reminder light on the instrument cluster. When the vehicle is started, this light flashes and a chime may come on to remind the driver to fasten their seat belt. Then the light stays on solid until the belt is buckled. This cycle may continue several times if the driver remains or becomes unbuckled while the vehicle is moving. If the driver seat belt is buckled, neither the light nor the chime comes on.
Front Passenger Seat Belt Reminder Light
The vehicle may have a front passenger seat belt reminder light near the passenger airbag status indicator. When the vehicle is started, this light flashes and a chime may come on to remind passengers to fasten their seat belts. Then the light stays on solid until the belt is buckled. This cycle continues several times if the front passenger remains or becomes unbuckled while the vehicle is moving. If the front passenger seat belt is buckled, neither the chime nor the light comes on. The front passenger seat belt reminder light and chime may come on if an object is put on the seat such as a briefcase, handbag, grocery bag, laptop, or other electronic device. To turn off the reminder light and/or chime, remove the object from the seat or buckle the seat belt.
Airbag Readiness Light
This light shows if there is an electrical problem with the airbag system. The system check includes the airbag sensor(s), the passenger sensing system, the pretensioners, the airbag modules, the wiring, and the crash sensing and diagnostic module. The airbag readiness light comes on for several seconds when the vehicle is started. If the light does not come on then, have it fixed immediately.
Warning
If the airbag readiness light stays on after the vehicle is started or comes on while driving, it means the airbag system might not be working properly. The airbags in the vehicle might not inflate in a crash, or they could even inflate without a crash. To help avoid injury, have the vehicle serviced right away.
If there is a problem with the airbag system, a Driver Information Center (DIC) message may also come on.
Passenger Airbag Status Indicator
The vehicle has a passenger sensing system. The overhead console has a passenger airbag status indicator.
When the vehicle is started, the passenger airbag status indicator will light ON and OFF, or the symbols for on and off, for several seconds as a system check. Then, after several more seconds, the status indicator will light either ON or OFF, or either the on or off symbol, to let you know the status of the front outboard passenger frontal airbag. If the word ON or the on symbol is lit on the passenger airbag status indicator, it means that the front outboard passenger frontal airbag is allowed to inflate. If the word OFF or the off symbol is lit on the passenger airbag status indicator, it means that the passenger sensing system has turned off the front outboard passenger frontal airbag. If, after several seconds, both status indicator lights remain on, or if there are no lights at all, there may be a problem with the lights or the passenger sensing system.
Warning
If the airbag readiness light ever comes on and stays on, it means that something may be wrong with the airbag system. To help avoid injury to yourself or others, have the vehicle serviced right away.
Charging System Light
The charging system light comes on briefly when the ignition is turned on, but the engine is not running, as a check to show the light is working. It should go out when the engine is started. If the light stays on or comes on while driving, there may be a problem with the electrical charging system. Have it checked by your dealer. Driving while this light is on could drain the battery. When this light comes on or is flashing, the Driver Information Center (DIC) also displays a message. If a short distance must be driven with the light on, be sure to turn off all accessories, such as the radio and air conditioner. Find a safe place to stop the vehicle.
Malfunction Indicator Lamp (Check Engine Light)
This light is part of the vehicle’s emission control onboard diagnostic system. If this light is on while the engine is running, a malfunction has been detected and the vehicle may require service. The light should come on to show that it is working when the ignition is on and the engine is not running. Malfunctions are often indicated by the system before any problem is noticeable. Being aware of the light and seeking service promptly when it comes on may prevent damage.
Caution
If the vehicle is driven continually with this light on, the emission control system may not work as well, the fuel economy may be lower, and the vehicle may not run smoothly. This could lead to costly repairs that might not be covered by the vehicle warranty. Modifications to the engine, transmission, exhaust, intake, or fuel system, or the use of replacement tires that do not meet the original tire specifications, can cause this light to come on. This could lead to costly repairs not covered by the vehicle warranty. This could also affect the vehicle’s ability to pass an Emissions Inspection/Maintenance test.
If the light is flashing: A malfunction has been detected that could damage the emission control system and increase vehicle emissions. Diagnosis and service may be required. To help prevent damage, reduce vehicle speed and avoid hard accelerations and uphill grades. If towing a trailer, reduce the amount of cargo being hauled as soon as possible. If the light continues to flash, find a safe place to park. Turn the vehicle off and wait at least 10 seconds before restarting the engine. If the light is still flashing, follow the previous guidelines and see your dealer for service as soon as possible.
If the light is on steady: A malfunction has been detected. Diagnosis and service may be required.
Check the following:
- If fuel has been added to the vehicle using the capless funnel adapter, make sure that it has been removed. The diagnostic system can detect if the adapter has been left installed in the vehicle, allowing fuel to evaporate into the atmosphere. A few driving trips with the adapter removed may turn off the light.
- Poor fuel quality can cause inefficient engine operation and poor driveability, which may go away once the engine is warmed up. If this occurs, change the fuel brand. It may require at least one full tank of the proper fuel to turn the light off. If the light remains on, see your dealer.
Emissions Inspection and Maintenance Programs
If the vehicle requires an Emissions Inspection/Maintenance test, the test equipment will likely connect to the vehicle’s Data Link Connector (DLC).
The DLC is under the instrument panel to the left of the steering wheel. Connecting devices that are not used to perform an Emissions Inspection/Maintenance test or to service the vehicle may affect vehicle operation.
The vehicle may not pass inspection if:
- The light is on when the engine is running.
- The light does not come on when the ignition is on while the engine is off.
- Critical emission control systems have not been completely diagnosed. If this happens, the vehicle will not be ready for inspection and might require several days of routine driving before the system is ready for inspection. This can happen if the 12-volt battery has recently been replaced or run down, or if the vehicle has been recently serviced.
Brake System Warning Light
This light should come on briefly when the vehicle is turned on. If it does not come on then, have it fixed so it will be ready to warn you if there is a problem. If the light comes on and stays on at start-up, there is a brake problem. Have the brake system inspected right away. If the light comes on while driving, pull off the road and stop carefully. If equipped with an electric brake boost, vehicle speed may be limited when the brake system warning light comes on. The brake pedal might be harder to push, or the brake pedal may go closer to the floor. It could take longer to stop. If the light is still on, have the vehicle towed for service.
Warning
The brake system might not be working properly if the brake system warning light is on. Driving with the brake system warning light on can lead to a crash. If the light is still on after the vehicle has been pulled off the road and carefully stopped, have the vehicle towed for service.
Electric Parking Brake Light
This light comes on when the parking brake is applied. If the light continues flashing after the parking brake is released, or while driving, there is a problem with the Electric Parking Brake system. A message may also be displayed in the Driver Information Center (DIC). If the light does not come on or remains flashing, see your dealer.
Service Electric Parking Brake Light
This light should come on briefly when starting the vehicle. If it does not come on, have it fixed so it will be ready to warn if there is a problem. If this light stays on, take the vehicle to your dealer as soon as possible. A message may also be displayed in the Driver Information Center (DIC).
Antilock Brake System (ABS) Warning Light
This warning light should come on briefly when the vehicle is turned on. If the light does not come on, have it fixed so it will be ready to warn if there is a problem. If the light comes on while driving, safely stop as soon as it is possible and turn off the vehicle. Then turn on the vehicle again to reset the system. If the ABS warning light stays on, or comes on again while driving, the vehicle needs service. A chime may also sound when the light stays on. If the ABS warning light is the only light on, the vehicle has regular brakes, but ABS is not functioning. If both the ABS warning light and the brake system warning light are on, ABS is not functioning and there is a problem with the regular brakes.
Four-Wheel-Drive Light
If equipped, the four-wheel-drive light displays what mode the vehicle is in. The light will show each mode: 2WD, 4HI, AUTO (all transfer cases); 4LOW, and N (two-speed transfer case only). The light will flash when a shift is in progress. Once the shift is complete the light will be steady. If the light turns amber, there may be a malfunction with the four-wheel-drive system. See your dealer.
Tow/Haul Mode Light
For vehicles with the Tow/Haul Mode feature, this light comes on when the Tow/ Haul Mode has been activated.
Hill Descent Control Light
If equipped, the Hill Descent Control light comes on when the system is ready for use. When the light flashes, the system is active.
Lane Keep Assist (LKA) Light
After the vehicle is started, this light turns off and stays off if LKA has not been turned on or is unavailable. If equipped, this light is white if LKA is turned on, but not ready to assist. This light is green if LKA is turned on and is ready to assist. LKA may assist by gently turning the steering wheel if the vehicle approaches a detected lane marking. The LKA light is amber when assisting. This light flashes amber as a Lane Departure Warning (LDW) alert, to indicate that the lane marking has been crossed. LKA will not assist or alert if the turn signal is active in the direction of lane departure, or if LKA detects that you are accelerating, braking, or actively steering.
Vehicle Ahead Indicator
If equipped, this indicator will display green when a vehicle is detected ahead and amber when you are following a vehicle ahead much too closely.
Pedestrian Ahead Indicator
If equipped, this indicator will display amber when a nearby pedestrian is detected in front of the vehicle.
Traction Off Light
This light comes on briefly when the vehicle is turned on. If it does not, have the vehicle serviced by your dealer. If the system is working normally, the indicator light then turns off. The traction off light comes on when the Traction Control System (TCS) has been turned off. If TCS is off, wheel spin is not limited unless necessary to help protect the driveline from damage. Adjust driving accordingly.
Traction Control System (TCS)/Electronic Stability Control Light
This light comes on briefly when the vehicle is turned on. If the light does not come on, have the vehicle serviced by your dealer. If the system is working normally, the indicator light turns off. If the light is on and not flashing, the TCS and potentially the ESC system are not fully operational and may not assist in maintaining control. Adjust driving accordingly. If the condition persists, see your dealer as soon as possible. A Driver Information Center (DIC) message may be displayed. The light flashes when the TCS and/or the ESC system is actively working.
Trailer Sway Control Light (Uplevel Cluster)
This light will flash when Trailer Sway Control is active.
Electronic Stability Control (ESC) Off Light
This light comes on briefly when the vehicle is turned on. If the light does not come on, have the vehicle serviced by your dealer. If the system is working normally, the indicator light then turns off. working normally, the indicator light then turns off. This light comes on when the Electronic Stability Control (ESC) system is turned off. If ESC and TCS are off, the systems do not assist in controlling the vehicle. Adjust driving accordingly.
Engine Coolant Temperature Warning Light
This light comes on briefly while starting the vehicle. If it does not, have the vehicle serviced by your dealer. If the system is working normally the indicator light goes off.
Caution
The engine coolant temperature warning light indicates that the vehicle has overheated. Driving with this light on can damage the engine and it may not be covered by the vehicle warranty. The engine coolant temperature warning light comes on when the engine has overheated. If this happens, pull over and turn off the engine as soon as possible.
Driver Mode Control Light
This light comes on when Sport Mode is selected.
This light comes on when Snow/Ice Mode is selected.
This light comes on when Terrain Mode is selected.
This light comes on when the Off-Road Mode is selected.
Tire Pressure Light
For vehicles with the Tire Pressure Monitor System (TPMS), this light comes on briefly when the engine is started. It provides information about tire pressures and the TPMS.
When the Light Is On Steady
This indicates that one or more of the tires are significantly underinflated. A Driver Information Center (DIC) tire pressure message may also be displayed. Stop as soon as possible, and inflate the tires to the pressure value shown on the Tire and Loading Information label.
When the Light Flashes First and Then Is On Steady
If the light flashes for about a minute and then stays on, there may be a problem with the TPMS. If the problem is not corrected, the light will come on at every ignition cycle.
Engine Oil Pressure Light (Uplevel Cluster)
Caution
Lack of proper engine oil maintenance can damage the engine. Driving with the engine oil low can also damage the engine. The repairs would not be covered by the vehicle warranty. Check the oil level as soon as possible. Add oil if required, but if the oil level is within the operating range and the oil pressure is still low, have the vehicle serviced. Always follow the maintenance schedule for changing engine oil.
This light should come on briefly as the engine is started. If it does not come on, have the vehicle serviced by your dealer. If the light comes on and stays on, it means that oil is not flowing through the engine properly. The vehicle could be low on oil and might have some other system problem. See your dealer.
Low Fuel Warning Light
This light is near the fuel gauge and comes on briefly when the ignition is turned on as a check to show it is working. It also comes on when the fuel tank is low on fuel. The light turns off when fuel is added. If it does not, have the vehicle serviced.
Security Light
The security light should come on briefly as the engine is started. If it does not come on, have the vehicle serviced by your dealer. If the system is working normally, the indicator light turns off. If the light stays on and the engine does not start, there could be a problem with the theft-deterrent system.
High-Beam On Light
This light comes on when the high-beam headlamps are in use.
IntelliBeam Light
This light comes on when the IntelliBeam system, if equipped, is enabled.
Front Fog Lamp Light
For vehicles with fog lamps, this light comes on when the fog lamps are on. The light goes out when the fog lamps are turned off.
Lamps On Reminder
This light comes on when the exterior lamps are in use, except when only the Daytime Running Lamps (DRL) are active.
Cruise Control Light
The cruise control light is white when the cruise control is on and ready, and turns green when the cruise control is set and active.
Adaptive Cruise Control Light
If equipped, this light is white when the Adaptive Cruise Control (ACC) is on and ready, and turns green when the ACC is set and active. When ACC is engaged and the driver accelerates, the indicator will turn blue.
Door Ajar Light
This light comes on when a door is open or not securely latched. Before driving, check that all doors are properly closed.
FAQs
The dashboard symbols in the 2021 GMC Sierra HD indicate various vehicle conditions and potential issues that require attention.
While some dashboard symbols indicate critical issues requiring immediate attention, others serve as informational alerts, such as reminders for low fuel or activated features.
Dashboard symbols are standardized across vehicles and cannot be customized; however, drivers can adjust certain settings related to alerts and notifications through the vehicle’s settings menu.
While many dashboard symbols are common across vehicles, there may be specific symbols unique to the 2021 GMC Sierra HD, reflecting its distinct features and functionalities.
Warning lights typically indicate potential issues or malfunctions, while indicator lights provide status updates or confirmations of activated features or systems.
Some dashboard symbols may disappear once the underlying issue is resolved or if the condition no longer applies, while others may require manual intervention or professional diagnostics to reset.
Yes, dashboard symbols may illuminate to remind drivers of routine maintenance tasks such as oil changes, tire rotations, or scheduled inspections.
Address critical warning lights indicating immediate safety concerns first, then proceed to investigate and resolve other illuminated symbols based on their severity and potential impact on vehicle performance.
While dashboard symbols offer initial alerts about potential issues, detailed diagnostic information may require connecting the vehicle to diagnostic tools or consulting a professional technician.
Yes, dashboard symbols may indicate issues with electronic systems such as the traction control system, adaptive cruise control, or advanced driver assistance features.
It’s advisable to routinely monitor the dashboard symbols each time you start your vehicle and periodically while driving to promptly address any emerging issues or alerts.
While dashboard symbols are standardized, some vehicles may offer language settings to display alerts and notifications in preferred languages or formats.
Yes, dashboard symbols may indicate issues with the fuel system, emissions controls, or exhaust components, alerting drivers to potential efficiency or environmental concerns.
Regularly familiarize yourself with dashboard symbols through online resources, vehicle forums, or manufacturer-provided guides to enhance your understanding and interpretation skills.
Useful Links
View Full PDF: GMC Sierra HD 2021 User Manual | Auto User Guide
2023 GMC SIERRA 1500 Specs, Price, Features, and Mileage (Brochure)