Well even if the lights aren't on, as long as the codes haven't been reset/erased, you can still pull the codes.
Do you know how to do it?
I'll try my best to explain it:
Put the key in the ignition...
-now turn it to where all the dash lights come on and you hear your fuel pump going (but don't start it).
-now click it back one...
-Do that 3 times, with the third stopping with all the dash lights on.
-Look at your odometer and it'll give you codes such as P0440, P0453, etc... Then it'll say "dONE"

Look those codes up online...
Hope that helped and it wasn't insultingly repetitive.