Can I drive with the check engine light on? Steady or flashing decides

What the warning actually means

The light alone does not tell you what is wrong. That takes reading the code, typically with an OBD-II scanner. A steady light is usually less urgent than a flashing one.

How the check engine light works

The car's computer monitors sensors throughout the engine and the emissions system. When a reading falls outside its expected range, it lights the check engine light and stores a diagnostic trouble code.

Common causes

• A loose or missing fuel cap, one of the most common reasons
• An engine fault the computer has stored as a code
• An emissions fault
• An active misfire, when the light is flashing

What to do now

1. Check whether the light is steady or flashing.
2. If it is flashing, reduce speed, drive as little as possible and have it checked as soon as possible.
3. If it is steady, check that the fuel cap is tightened fully.
4. Get the code read soon, typically with an OBD-II scanner.
5. If the light does not clear after a few drive cycles with a tight cap, have the fuel system checked.

Steady or flashing?

• Steady check engine light: usually yes, keep driving for now, and get the code read soon.
• Flashing check engine light: not as normal, because an active misfire can damage the catalytic converter.
• Came on right after refueling: check the fuel cap first.

What people often get wrong

Assuming the check engine light is probably nothing. Sometimes that is true, but the only way to know is to get the code read.

When the car must go to a workshop

Have it checked as soon as possible if the light flashes, and soon if it stays on steady.

Read next

• Flashing check engine light: slow down, this one is urgent
• Check engine light after refueling: check the fuel cap first
• P0300: misfire on more than one cylinder

This page is general information and does not replace a professional assessment. Symbols, codes and behaviour vary between makes. Always check the handbook for your own car.