An OBD code (short for on-board diagnostics) is a trouble code your car's computer stores when it detects a problem. A scan tool reads the code — for example P0300 — and the code points to the system that needs attention. Every car sold in the US since 1996 uses the same OBD-II system.

Plug an OBD-II scanner into the diagnostic port under your dashboard, usually on the driver's side. Many auto parts stores will read the code for free, and cheap Bluetooth scanners work with a phone app. Write down the exact code, then look it up here.

It depends on the code. A loose gas cap (P0455) is usually safe for a short trip. A flashing check engine light, or a high-severity code like P0300, means stop driving and get it checked — driving can cause expensive damage. Every code page here tells you plainly whether it is safe to drive.

P0300 means the engine is misfiring in more than one cylinder. Common causes are worn spark plugs, bad ignition coils, or a vacuum leak. It is a high-severity code: the car can overheat the catalytic converter, so get it checked right away.

Yes. In the US, safety recalls are repaired free of charge by the manufacturer at an authorized dealer, no matter how old the car is. Check your car with our Recalls & Complaints tool, which uses the official NHTSA database.

Yes. The OBD code lookup and every tool on this site are free, with no signup and no tracking.