Check Engine Light: Causes and What to Do
Written by Muneeb Rana · Last updated 21 October 2026
Quick answer: A check engine light means the engine computer has logged a fault, from a loose fuel cap to a misfire or failing sensor. A steady light means book a diagnosis soon; a flashing light usually means a severe misfire that can damage the catalytic converter, so reduce speed and stop driving as soon as it's safe.
TL;DR
- Colour: Amber/yellow (sometimes flashing).
- Steady: get it checked soon. Flashing: slow down and stop driving as soon as it's safe.
- Fix the cause rather than just clearing the light, and log the repair.
The check engine light is one of the dashboard warnings drivers search for most. This guide covers what it looks like, what it means, how urgent it is and what to do, in plain English. Your owner's manual has the exact symbol and advice for your car.
What does the check engine light look like?
| Symbol | An engine outline, sometimes with the word CHECK |
| Colour | Amber/yellow (sometimes flashing) |
| How urgent | Steady: get it checked soon. Flashing: slow down and stop driving as soon as it's safe. |
Warning lights follow a rough traffic-light code: red means a serious problem or safety issue, so stop when it's safe; amber or yellow means something needs attention soon; green or blue is information only. See the full dashboard warning lights guide for every common symbol.
What the check engine light means
AAA points out that ignoring a check engine light can turn a cheap fix into an expensive one, and in many US states and countries a lit check engine light means the car fails its emissions inspection.
Common causes:
- A loose, damaged or missing fuel cap
- A faulty oxygen (O2) sensor
- Worn spark plugs or ignition coils causing misfires
- A failing catalytic converter
- A mass airflow (MAF) sensor fault
- Vacuum or evaporative system (EVAP) leaks
What to do when the check engine light comes on
- Check whether the light is steady or flashing.
- If flashing, or the car runs rough, slow down and stop when it's safe; don't keep driving hard.
- If steady, tighten the fuel cap until it clicks; the light may take a few drive cycles to clear.
- Get the fault code read. Many parts stores read codes free, or use an inexpensive OBD-II scanner.
- Fix the cause, then log the repair and the code so you can spot repeat faults.
Can you drive with the check engine light on?
With a steady light and no other symptoms, usually yes for a short distance to a shop. With a flashing light, overheating, low oil pressure or a loss of power, no.
If you're not sure, treat it as the more serious case. A tow costs far less than a ruined engine, gearbox or set of brakes. If several warning lights come on at once, that often points to an electrical or charging problem; see the check engine light guide and the battery light page.
How to reset or clear it
Don't just clear the light. Most warning lights go out on their own once the fault is fixed, sometimes after a few drive cycles. Clearing a code with a scanner without fixing the cause only hides the problem until it returns, and it can make an emissions test fail because the car's readiness monitors reset.
Keep a record of warning lights and repairs
Write down the date, odometer reading, what the light looked like, the fault code if you had it read, and what fixed it. If the same light comes back, that history saves diagnosis time and money. In CarO you can log the repair and its cost in the car repair log, and set a follow-up with the service reminder tool. For a routine check that catches problems before a light comes on, use our car maintenance checklist. Related: spark plug guide and maintenance cost calculator.
Download CarO free on the App Store or Google Play. Free with ads; optional in-app purchases.
Sources
- AAA: The Check Engine Light, Common Causes and How to Fix It: www.aaa.com (accessed 21 October 2026)
- Consumer Reports: What the Dashboard Warning Lights Mean in Your Car: www.consumerreports.org (accessed 21 October 2026)
- The AA: Dashboard warning lights and what they mean: www.theaa.com (accessed 21 October 2026)
Disclaimer: CarO and this website give general car-care information, not professional advice. Maintenance intervals and specifications vary by vehicle, so always follow your owner's manual and a qualified mechanic. Mileage and cost figures are estimates; check local tax rules before using any log for deductions.
FAQ
What does the check engine light mean?
A check engine light means the engine computer has logged a fault, from a loose fuel cap to a misfire or failing sensor.
Is it safe to drive with the check engine light on?
With a steady light and no other symptoms, usually yes for a short distance to a shop. With a flashing light, overheating, low oil pressure or a loss of power, no.
What colour is the check engine light?
Amber/yellow (sometimes flashing). Red warnings mean stop when safe, amber means get it checked soon, and green or blue lights are information only.
How do I turn off the check engine light?
Fix the underlying cause; the light usually goes out by itself, sometimes after a few drive cycles. Clearing the code without a repair only hides the problem.
How much does it cost to fix the check engine light?
It depends entirely on the cause, from nothing for a loose cap or released parking brake to a major repair. Get the fault diagnosed and ask for an itemized estimate before approving work.
Track this in CarO
CarO is a free car maintenance tracker app for iPhone and Android that keeps a full service history, reminds you about oil changes and inspections by mileage or date, and logs fuel fill-ups with MPG, odometer readings and car expenses for every vehicle you own. Logs are stored in the cloud and can be exported as CSV.
