Check engine light on — how to read codes without a scanner?

AutoZone, O'Reilly, and Advance Auto will read your codes for free. Just drive there and ask. They'll plug in their scanner and give you the code numbers. For owning your own, a Bluetooth ELM327 adapter ( on Amazon) plus the free Torque app on Android gives you codes plus live data. Best  you'll ever spend on car maintenance.

Quick tip: some auto parts stores will clear the code for you too, but I'd recommend writing down the code first and looking it up before clearing it. A code is your car telling you something is wrong — clearing it without fixing the problem just delays the inevitable.