Dashboard Warning Lights
Don't ignore that light on your dashboard. Browse our guide to the 25 most common warning lights, learn what they mean, and find out how urgent the issue is and what repairs might cost.
Critical
Caution
Informational
Critical
Oil Pressure Warning
Engine oil pressure has dropped below safe levels. This can mean low oil level, a failing oil pump, a clogged oil pickup screen, or worn engine bearings. Running an engine without oil pressure causes catastrophic damage in seconds to minutes.
Cost: $0 – $8,000Details
Critical
Battery / Charging System Warning
The alternator is not charging the battery. Your vehicle is running on battery power alone, and once the battery drains, the engine will stall and all electrical systems will shut down. This is NOT a battery problem — it's a charging system problem.
Cost: $100 – $800Details
Critical
Brake System Warning
Can indicate engaged parking brake, low brake fluid level, a fault in the ABS system, or a serious hydraulic failure. In some vehicles, this light also serves as the parking brake indicator.
Cost: $80 – $2,000Details
Critical
Engine Coolant Temperature Warning
Engine coolant temperature has exceeded safe operating range. Overheating can warp cylinder heads, blow head gaskets, and cause permanent engine damage. This light may be red (overheating) or blue (engine cold — normal on startup).
Cost: $50 – $3,500Details
Critical
Reduced Engine Power / Limp Mode
The engine ECU has detected a serious fault and has limited engine output to protect the engine, transmission, or emissions system. The vehicle may have severely reduced acceleration and limited top speed. This is sometimes called 'limp home mode.'
Cost: $100 – $3,000Details
Critical
Electric Vehicle System Warning (EV/Hybrid)
The high-voltage electric drive system has a fault. This can affect the traction battery, electric motor, power electronics, or charging system. The vehicle may have reduced power, may not charge, or may not start.
Cost: $200 – $15,000Details
Critical
Transmission Temperature Warning
Transmission fluid temperature has exceeded safe operating range. Overheated transmission fluid loses its lubricating properties and can cause permanent damage to clutches, bands, and seals. This is most common when towing heavy loads or in stop-and-go traffic in hot weather.
Cost: $100 – $4,000Details
Critical
Hood Open Warning
The hood is not fully latched. Driving with an unlatched hood can result in the hood flying open at speed, completely blocking forward visibility — an extremely dangerous situation.
Cost: $0 – $150Details
Critical
Timing Belt Replacement Due
The timing belt replacement interval has been reached. This is a critical maintenance item — if the timing belt breaks while driving, the engine will suffer catastrophic damage (pistons hitting valves) on interference engines. Most vehicles require timing belt replacement every 60,000-105,000 miles.
Cost: $500 – $1,500Details
Caution
Check Engine Light (MIL)
The Malfunction Indicator Lamp means your vehicle's ECU has detected a fault in the engine, emissions, or fuel system. This is the most common warning light, covering everything from a loose gas cap to a failed catalytic converter.
Cost: $0 – $3,000Details
Caution
Tire Pressure Monitoring System (TPMS)
One or more tires has low pressure (solid light) or the TPMS system itself has a fault (flashing light). Underinflated tires reduce fuel economy, increase stopping distance, and can cause blowouts at highway speeds.
Cost: $0 – $400Details
Caution
Anti-lock Braking System (ABS) Warning
The ABS system has detected a fault and is disabled. Your regular brakes still work, but the anti-lock function (which prevents wheel lockup during emergency braking) is not available. The vehicle may also disable traction control and stability control when ABS fails.
Cost: $100 – $1,500Details
Caution
Supplemental Restraint System (SRS / Airbag)
The airbag system has a fault. In a collision, one or more airbags may not deploy, or may deploy unexpectedly. This is a passive safety system — the vehicle drives normally, but occupant protection is compromised.
Cost: $50 – $1,500Details
Caution
Traction Control / Stability Control (TCS/ESC)
The traction control or electronic stability control system has been disabled, either by a switch or due to a fault. These systems help prevent wheel spin and loss of control. The light may flash during active intervention (normal) or stay solid (fault).
Cost: $50 – $1,200Details
Caution
Electric Power Steering (EPS) Warning
The electric power steering system has a fault. Steering effort will increase significantly, especially at low speeds and during parking maneuvers. Hydraulic power steering uses a different warning (see Power Steering Fluid).
Cost: $200 – $2,500Details
Caution
Security / Immobilizer / Anti-Theft
The vehicle's immobilizer system does not recognize the key or there is a security system fault. This may prevent the engine from starting, or the light may come on while driving, indicating a system fault.
Cost: $50 – $1,200Details
Caution
Low Fuel Level
Fuel level is critically low — typically 1-2 gallons remaining. Running out of fuel can damage the fuel pump (which uses fuel for cooling), especially on modern direct-injection engines.
Cost: $30 – $150Details
Caution
Electric Parking Brake (EPB)
The electric parking brake has a fault or needs service. The parking brake may not engage or disengage properly. In some vehicles, a flashing EPB light indicates the parking brake is in service/maintenance mode for brake pad replacement.
Cost: $100 – $1,200Details
Caution
Diesel Particulate Filter (DPF) Warning
The diesel particulate filter is becoming clogged with soot and needs regeneration. If ignored, the DPF can become irreversibly blocked, requiring expensive replacement. This light primarily affects modern diesel vehicles (2009+).
Cost: $100 – $3,500Details
Caution
AdBlue / Diesel Exhaust Fluid (DEF) Warning
The diesel exhaust fluid (AdBlue/DEF) is low. This is used in Selective Catalytic Reduction (SCR) systems to reduce NOx emissions. Running completely out may prevent the engine from starting (anti-tamper regulation).
Cost: $10 – $50Details
Caution
Fuel Filter Water (Diesel)
Water has accumulated in the diesel fuel filter/water separator and needs to be drained. Water in diesel fuel can cause injector damage, fuel pump failure, and microbial growth in the fuel tank.
Cost: $0 – $500Details
Caution
AWD / 4WD System Warning
The all-wheel drive or four-wheel drive system has a fault. The vehicle may default to front-wheel drive (or rear-wheel drive) only. The system may have disabled itself to protect the drivetrain.
Cost: $100 – $3,000Details
Caution
Air Suspension / Ride Height Warning
The air suspension system has a fault. The vehicle may sit unevenly, ride harshly, or be unable to maintain proper ride height. This primarily affects luxury SUVs (Range Rover, Mercedes, Audi) and trucks with air-ride systems.
Cost: $300 – $3,000Details
Caution
Exterior Light Failure
One or more exterior lights is not functioning — headlight, brake light, turn signal, or running light. This is both a safety hazard and a traffic violation in all US states.
Cost: $5 – $500Details
Caution
Adaptive / Electronic Suspension Warning
The adaptive damping or electronic suspension control system has a fault. The vehicle may default to a firm ride and lose the ability to switch between comfort/sport modes. This affects vehicles with magnetic ride, air suspension without ride height issues, or electronically controlled dampers.
Cost: $200 – $2,000Details
Caution
Emissions System Warning
The vehicle's emissions control system has a fault. This is common on diesel vehicles and some newer gasoline vehicles with enhanced emissions monitoring. In states with emissions testing, this light will cause a failed inspection.
Cost: $100 – $2,500Details
Caution
Active Rear Spoiler / Aerodynamic System
The active rear spoiler or aerodynamic system has a fault. The spoiler may not deploy at speed, affecting high-speed stability. This primarily affects sports cars with active aero (e.g., Porsche, Audi TT, Bugatti).
Cost: $300 – $3,000Details
Caution
Trailer Connection / Trailer Light Fault
The vehicle has detected a trailer electrical connection, or there is a fault with the trailer lighting circuit. A faulty trailer light is both a safety hazard and a traffic violation.
Cost: $0 – $200Details
Caution
Brake Pad Wear Indicator
The brake pads have worn to their minimum thickness and need replacement. Most modern vehicles have electronic wear sensors embedded in the pads. Continuing to drive with worn pads will damage the brake rotors, turning a $200 pad job into a $500+ pad-and-rotor job.
Cost: $150 – $500Details
Caution
Headlight Leveling / Adaptive Headlight
The automatic headlight leveling system or adaptive (swiveling) headlight system has a fault. Headlights may be aimed too high (blinding oncoming traffic) or too low (reduced visibility). Adaptive headlights may not swivel with steering input.
Cost: $100 – $1,500Details
Caution
Forward Collision Warning / Automatic Emergency Braking
The forward collision warning or automatic emergency braking system is temporarily unavailable or has a fault. The vehicle will not provide collision warnings or automatic braking while this system is offline.
Cost: $100 – $2,500Details
Caution
Regenerative Braking System (EV/Hybrid)
The regenerative braking system is reduced or unavailable. The vehicle may rely more heavily on friction brakes, reducing energy recovery and range. Brake pedal feel may change — this is normal and the friction brakes still work.
Cost: $0 – $2,000Details
Caution
Catalytic Converter / Emissions System
The catalytic converter or downstream emissions system has a fault. This may indicate a failing catalytic converter, which is one of the most expensive emissions repairs and often a symptom of an underlying engine issue (misfire, oil burning, rich fuel mixture) that damaged the converter.
Cost: $500 – $3,000Details
Informational
Glow Plug Indicator (Diesel)
This light has two functions on diesel engines: 1) Preheating: light is on while glow plugs warm up before starting (normal, wait until it goes out before cranking). 2) Fault: light stays on or flashes while driving — indicates a glow plug, glow plug relay, or engine management fault.
Cost: $80 – $600Details
Informational
Service Vehicle Soon
The vehicle's onboard maintenance minder has determined that scheduled maintenance is due — oil change, tire rotation, inspection, etc. This is different from a check engine light and is NOT indicating a fault. It's based on mileage and/or time since the last service.
Cost: $50 – $300Details
Informational
Oil Change Reminder
The oil life monitor indicates the engine oil has degraded and needs changing. Modern vehicles calculate oil life based on driving conditions — short trips and towing deplete oil life faster than highway driving.
Cost: $35 – $120Details
Informational
Windshield Washer Fluid Low
The windshield washer fluid reservoir is low or empty. Running the washer pump without fluid can damage the pump motor over time.
Cost: $3 – $10Details
Informational
Door / Trunk / Hood Ajar
One or more doors, the trunk/hatch, or the hood is not fully latched. Driving with a door unlatched is a safety hazard — the door could open at speed.
Cost: $0 – $200Details
Informational
Seat Belt Reminder
A seat belt is not fastened in an occupied seat. This light is often accompanied by an audible chime. In most US states, front-seat belt use is legally required.
Cost: $0 – $300Details
Informational
Cruise Control / Adaptive Cruise Control
Cruise control is active (green/white light) or there is a fault in the cruise control system (amber/yellow light). Adaptive cruise control may also be unavailable if the radar sensor is blocked by snow, ice, or mud.
Cost: $50 – $800Details
Informational
Lane Departure Warning (LDW) / Lane Keep Assist
The lane departure warning or lane keep assist system is active (green) or has a fault (amber). This system uses a forward-facing camera (usually behind the windshield) to detect lane markings.
Cost: $100 – $1,200Details
Informational
Automatic High Beam
The automatic high beam system is active (green with 'A' symbol) or has a fault (amber). This system automatically switches between high and low beams based on oncoming traffic and ambient lighting.
Cost: $50 – $500Details
Informational
Blind Spot Monitor / Rear Cross Traffic Alert
The blind spot monitoring or rear cross traffic alert system is temporarily unavailable or has a fault. These systems use radar sensors (usually behind the rear bumper) to detect vehicles in adjacent lanes.
Cost: $100 – $1,500Details
Informational
Auto Start-Stop / Mild Hybrid Warning
The auto start-stop system or mild-hybrid system has a fault or has been temporarily disabled. This system automatically shuts off the engine when stopped and restarts when the brake is released to save fuel.
Cost: $150 – $500Details
Informational
Key Fob Battery Low / Key Not Detected
The vehicle is having difficulty detecting the key fob. The fob battery may be low, or there may be signal interference. On keyless start vehicles, this may prevent push-button starting.
Cost: $2 – $300Details
Informational
Electronic Stability Program (ESP) Off
The electronic stability program has been manually turned off via the ESP button, or is temporarily disabled due to a fault. ESP helps prevent skidding and loss of control by applying individual brakes and reducing engine power.
Cost: $0 – $800Details
Informational
Passenger Airbag Off
The front passenger airbag has been automatically disabled because the seat occupancy sensor detects no passenger, or a small child/child seat. This is NORMAL behavior. The light should turn off when an adult sits in the passenger seat.
Cost: $0 – $800Details
Informational
Night Vision System
The night vision or thermal imaging system is unavailable or has a fault. This is a luxury vehicle feature (BMW, Mercedes, Audi, Cadillac) that uses an infrared camera to detect pedestrians and animals beyond headlight range.
Cost: $200 – $3,000Details
Informational
Hill Descent Control
Hill descent control is active (green light — vehicle is automatically controlling speed on a steep descent) or the system has a fault (amber light). This system is common on trucks and SUVs and uses ABS to maintain a constant low speed downhill.
Cost: $50 – $500Details
Informational
Electric Parking Brake Service Mode
The electric parking brake is in service/maintenance mode. This mode must be activated before performing rear brake pad replacement, as the EPB actuator must be electronically retracted. Attempting to compress the caliper pistons without activating service mode will damage the EPB actuator.
Cost: $0 – $300Details