Cars and light trucks sold in the US from 1996 on have a standard OBD-II port, usually under the dashboard near the steering column.
Step by step
- Plug in a code reader or Bluetooth scanner with the ignition on (engine off is fine).
- Write down every code, including pending and permanent codes, and any freeze-frame data it shows.
- Look up each code's meaning, but treat it as a starting point, not a diagnosis.
Don't clear the codes yet
Clearing codes turns the light off but erases information the shop could use, and the problem is usually still there. Leave them stored until the car is diagnosed.
No reader? Many auto parts stores will read codes for free. Want your own? See our guide to the best code readers for your phone.