GMC Sierra Denali 2500HD/3500HD Warning Lights: What They Mean

Red: stop or act now

Airbag Readiness Light

If it stays on after starting or comes on while driving, the airbag system may not work properly; airbags might not inflate in a crash.
What to do: Have the vehicle serviced right away. PDF page 116

Engine Coolant Temperature Warning Light

The engine has overheated. Driving with the light on can damage the engine.
What to do: Pull over and turn off the engine as soon as possible. PDF page 122

Amber: check soon

ABS Warning Light

If it stays on or returns while driving, the vehicle needs service. If alone, regular brakes work but ABS does not.
What to do: Stop safely, turn the vehicle off and on to reset. If the light persists, see your dealer. PDF page 120

Four-Wheel-Drive Light

Shows the drive mode and flashes during a shift. If it turns amber, the four-wheel-drive system may have a malfunction.
What to do: See your dealer. PDF page 120

Lane Departure Warning (LDW) Light

Green when LDW is on and ready. Flashing amber means a lane marking was crossed without a turn signal. PDF page 120

Vehicle Ahead Indicator

Green when a vehicle is detected ahead; amber when you are following much too closely. PDF page 120

Other warnings and indicators

Engine Oil Pressure Light (Uplevel Cluster)

If it comes on and stays on, oil is not flowing through the engine properly; the vehicle may be low on oil.
What to do: Check the oil level and add oil if needed. If the light persists, see your dealer. PDF page 123

Traction Control System (TCS)/Electronic Stability Control Light

Steady: TCS and possibly ESC are not fully operational. Flashing: the system is actively working.
What to do: Adjust driving accordingly. If the condition persists, see your dealer as soon as possible. PDF page 121

Low Fuel Warning Light

Comes on when the fuel gauge nears empty. It turns off when fuel is added.
What to do: Add fuel. If the light stays on afterward, have the vehicle serviced. PDF page 123

Traction Off Light

Traction Control System has been turned off, so wheel spin is not limited except to protect the driveline.
What to do: Adjust driving accordingly. PDF page 121

Passenger Airbag Status Indicator

ON means the front passenger airbag may inflate; OFF means the sensing system turned it off. Both or neither lit may mean a problem.
What to do: If both lights stay on or none light, see your dealer for service. PDF page 116

Hill Descent Control Light

Comes on when the system is ready for use; flashing means the system is active. PDF page 120

Trailer Sway Control Light (Uplevel Cluster)

Flashes when Trailer Sway Control is active. PDF page 121

Driver Mode Control Light

Comes on when Snow Mode, Off-Road Mode, or Tow/Haul Mode is selected. PDF page 122

Summarized in our own words from the 2022 GMC Sierra Denali 2500HD/3500HD owner's manual (AI-assisted; every light name was matched against its cited page 2026-10-18). Your vehicle may not have every light, and other years can differ. A red warning that stays on usually means stop safely and check: your manual has the final word.