What do all the service lights mean?

Dashboard service lights indicate maintenance needs or faults in your vehicle. They alert you to issues from routine oil changes to serious system failures, and the exact meaning depends on the car's make and model.

In this guide, we explain the most common service and warning lights you’re likely to encounter, what they signal, and how to respond. We also outline steps for safety and when to call a technician, so you can navigate a dashboard full of symbols with more confidence.

Common service lights and what they mean

The following indicators cover the lights most drivers see on modern passenger cars. Each light has a general meaning, but the exact icon and color can vary by manufacturer. If a light appears, consult your owner's manual for model-specific guidance.

• Check Engine / Malfunction Indicator Lamp (MIL) — signals an engine or emission-control fault that should be diagnosed with an OBD-II scan. Do not ignore if it stays solid or starts flashing, especially while driving.


• Oil Pressure Warning — indicates dangerously low oil pressure; continuing to drive can cause severe engine damage. Stop safely and check oil level, or call for assistance.


• Oil Change / Maintenance Required — reminds you that scheduled maintenance is due or overdue, such as an oil change; reset after service.


• Battery / Charging System — alerts to a failing alternator, weak battery, or charging fault that can leave you stranded.


• Brake System / ABS — can indicate brake fluid level low, a fault in the braking system, or the anti-lock braking system; seek service if the light stays on or glows red.


• Traction Control / ESC — warns of a fault in traction control or stability control systems; driving is still possible but with reduced safety features.


• Airbag / SRS — indicates a fault in the supplemental restraint system; have the airbag system checked promptly.


• Seat Belt Reminder — alerts that a seat belt is not fastened for the occupants; ensure belts are securely fastened.


• Engine Overheating / Coolant Temperature — signals the engine is running hot; pull over safely, check coolant levels if possible, and seek help if the temperature continues to rise.


• Coolant Level Low or Coolant Temperature High — may appear as a separate symbol or integrated into the temperature warning; involves coolant level or overheating concerns.


• Low Fuel — indicates the remaining fuel is below the reserve threshold; refuel soon.


• Tire Pressure Monitoring System (TPMS) — shows one or more tires are under-inflated; check tire pressures and inflate to the recommended level.


• Service Vehicle Soon / Maintenance Due — generic reminder that routine service is due or upcoming; plan a service visit.


• Diesel Exhaust Fluid (DEF) Low / AdBlue — common on newer diesel engines, signaling the DEF reservoir is low and needs topping up to maintain emissions compliance.


• Diesel Particulate Filter (DPF) Warning / Regen Required — on diesel models, indicates the DPF is becoming clogged and may require a regeneration cycle or service if the light persists.


• Transmission Temperature / Transmission Fault — warns of abnormal transmission temperature or a fault in transmission control; pull over if safe and seek service if indicator stays on.


• Electronic Parking Brake / Brake System Warning — can indicate the electronic parking brake is engaged or there’s a fault in the parking brake system.

The exact icons, colors, and the combination of indicators can vary by brand. In particular, some items like maintenance reminders blend with branded systems (for example, "Maintenance due" in European or Japanese makes). Always check the owner’s manual for precise definitions relevant to your vehicle.

Understanding the color cues

Red lights generally demand immediate attention and indicate a condition critical to safety or engine integrity. Amber or yellow lights suggest a fault or required maintenance that should be addressed soon, but driving may be possible with caution. Green or blue indicators are usually informational, confirming system activity (like headlights or cruise control).

When a light appears, here’s a quick sense of urgency: red lights usually require stopping safely and addressing the issue before continuing; amber lights call for prompt service or checking the condition as soon as convenient; green/blue lights are typically confirmations or status indicators.

What to do when a service light appears

When a light comes on, follow these general steps to stay safe and minimize damage. The actions depend on the light and whether it stays on or flashes.

Before taking action, you should:

1. Safely pull over to a secure location if the vehicle is behaving unusually, smells odd, or the engine temperature is rising.


2. Check your owner's manual for the specific meaning of the light and recommended actions for your model.


3. Check obvious issues you can safely verify (oil level, coolant level, tire pressures, and fuel level).


4. If the light is red or flashing, do not continue driving aggressively; limit speed and get the vehicle inspected as soon as possible.


5. Schedule service with a qualified technician if the light persists after initial checks or if you cannot identify a safe repair on your own.

In short, treat red lights as urgent warnings and amber lights as reminders to seek service soon. Ignoring these indicators can lead to more extensive or costly damage or compromise safety.

Manufacturer and model caveats

Vehicle dashboards vary by manufacturer. Some brands use different icons for similar problems, and some combine maintenance reminders into a single “Service” symbol. If in doubt, rely on your owner's manual or a dealership service professional for model-specific interpretations.

Summary

Dashboard service lights are essential safety and maintenance cues that help drivers know when to check oil, tires, brakes, the battery, or more complex systems like airbags and emissions controls. The most common lights cover engine faults, oil and coolant issues, brake and traction systems, tire pressures, and maintenance reminders. Color and icon design differ by maker, so always consult your manual for precise meanings. When a light appears, respond according to its urgency: red for immediate danger, amber for prompt service, and green/blue for informational status. Regular maintenance and prompt attention to warnings can prevent breakdowns and keep you safer on the road.

What is the most serious warning light in a car?

#1: Check Engine Light
The check engine light is something you shouldn't ignore because there are several possible reasons why this light could appear. Most common reasons include issues with the vehicle's emission system, engine components, or fuel compartment.

Why are all my service lights on?

Electrical or Battery Issues – A weak or failing battery can cause multiple sensors to misfire, leading to multiple lights appearing. Faulty Sensors or Wiring Problems – If the sensors that monitor various systems fail or their wiring becomes damaged, your car's computer may mistakenly trigger multiple warnings.

What is the master warning ⚠?

The master warning light, a triangle with an exclamation mark, is a general warning that indicates a malfunction in one or more of the vehicle's safety or advanced electronic systems. It can signal issues ranging from low windshield washer fluid to serious problems with the engine, brakes, or stability control. When this light appears, you should check the car's display for a specific message and consult the owner's manual to identify the exact problem and determine if it is safe to drive.
 
This video explains what the master warning light means and what actions you should take: 20sToyota of SeattleYouTube · May 3, 2018
Possible causes

• Low fluid levels: Windshield washer fluid, brake fluid, or oil can be a common trigger. 
• System malfunctions: It can indicate a problem with advanced systems like the electronic stability control, anti-lock brakes, or power steering. 
• Sensor issues: Faulty sensors related to various systems can also trigger the light. 
• Routine maintenance needed: It can simply be a reminder that a scheduled service is due. 

You can watch this video to learn more about the causes of the master warning light, such as low washer fluid and open doors: 41sMotor MatchupsYouTube · Dec 21, 2024
What to do

1. Check your display: Look at the car's information display for a more specific message that often accompanies the master warning light. 
2. Consult the owner's manual: The manual will provide a guide to all dashboard symbols and explain what the master warning light means for your specific vehicle model. 
3. Check basic fluid levels: If there are no other obvious messages, check your windshield washer fluid, and then your brake fluid. 
4. Do not ignore it: Even if it turns out to be a minor issue, like low washer fluid, it's important to address the cause to turn the light off and prevent future issues. 
5. Seek professional help: If you cannot determine the cause or if the light indicates a serious problem, it is best to have your car inspected by a qualified mechanic. 

This video shows how to diagnose and reset the master warning light: 1mDashboard warning lights YouTube · Aug 6, 2025

What do the service lights mean on a car?

Orange/yellow warning lights generally signify that your vehicle needs to be serviced or repaired soon. These warnings are less urgent than if you have a red and/or flashing light. A red light means that you should take action immediately!