Check Engine Light On? Here's What It Means

The check engine light strikes fear into drivers, but it doesn't always mean disaster. Here's a plain-English guide.

Most Common Causes

1. Loose Gas Cap

Causes an EVAP leak code. Tighten it and drive for a day. If the light goes off, you're good.

2. Oxygen (O2) Sensor — $150-300

Reduces fuel economy and can damage your catalytic converter if ignored.

3. Catalytic Converter — $800-2,500

Usually fails because an upstream problem was ignored. This is why you shouldn't ignore check engine lights.

4. Mass Airflow Sensor — $200-400

Causes rough idle, poor acceleration, and reduced fuel economy.

5. Spark Plugs/Ignition Coils — $100-300

Cause misfires and rough running.

Solid vs. Flashing Light

Solid: Something needs attention but isn't critical. Schedule a diagnostic soon.

Flashing: Active misfires — reduce speed and get it diagnosed ASAP.

Why You Shouldn't Ignore It

A $200 O2 sensor ignored for a year becomes a $2,000 catalytic converter replacement.