That dreaded orange light on your dashboard — the Check Engine Light (CEL) — can mean dozens of different things. Here’s how to diagnose it yourself before heading to an expensive mechanic.
Get an OBD2 Scanner
Every car made after 1996 has an OBD2 port, usually located under the dashboard on the driver’s side. A basic OBD2 scanner costs as little as $20 and plugs directly into this port to read fault codes.
Most Common Error Codes
- P0300 — Random/Multiple Cylinder Misfire. Often caused by bad spark plugs or ignition coils.
- P0420 — Catalyst System Efficiency Below Threshold. Usually a failing catalytic converter.
- P0171 — System Too Lean (Bank 1). Could be a vacuum leak or faulty mass airflow sensor.
- P0442 — Evaporative Emission Control System Leak Detected. Often just a loose gas cap!
- P0113 — Intake Air Temperature Sensor High Input. Usually a dirty or failing sensor.
When Is It Safe to Keep Driving?
If the light is steady and the car drives normally, you likely have time to diagnose it properly. If the light is flashing or blinking, stop driving immediately — a flashing CEL usually indicates an active misfire that can damage your catalytic converter.
