A lot of the earlier year trucks did that. My 2001 I sold if you turned the ignition on then off when you got to the third on it would read the codes out using the odometer mileage lights. I haven't had any or for that fact My 13 has over 3000 miles on it now without even a hiccup. Worst mileage was 15.3 and best has been 18.6. I haven't put any highway miles on yet but I'm betting it will do around 22 maybe more. I Love this truck!