Check Engine Light
The engine computer has detected a fault in the engine, emissions, or fuel system.
What it means
Also called the malfunction indicator lamp (MIL). It means the onboard diagnostics system (OBD-II) has stored a fault code. Causes range from a loose gas cap to a failing catalytic converter. A flashing check engine light indicates an active misfire that can damage the catalytic converter — treat that as urgent.
Can you keep driving?
If the light is steady and the car drives normally, you can usually drive cautiously to a mechanic or parts store for a code scan within a few days. If the light is flashing, or the engine runs rough, loses power, or overheats, pull over and shut it off.
What to do now
- 1
Check that the gas cap is tight — a loose cap is a common trigger, and the light may go out after a few drives.
- 2
Note any symptoms: rough idle, poor power, strange smells, or worse fuel economy.
- 3
Get the fault codes read — many auto parts stores scan OBD-II codes free, or use an inexpensive Bluetooth scanner.
- 4
If the light is flashing, stop driving and arrange a tow to prevent catalytic converter damage.
Likely causes
- • Loose or faulty gas cap
- • Failing oxygen sensor
- • Worn spark plugs or ignition coils
- • Faulty mass airflow sensor
- • Failing catalytic converter
- • Vacuum or EVAP system leak
Typical fix cost
$0 (tighten gas cap) to $150–$450 for common sensors; $1,000+ for catalytic converter work
Ranges reflect mainstream US parts-and-labor pricing; your vehicle and region will vary.