search this site's forum archive for "pedal dance", you will find the instructions on clearing codes without the laptop, on these trucks.
you may have set the "major code" function, but it will clear with the pedal dance, as long as what ever set the code is fixed, AND the code is not related to a foot pedal's operation.
You are correct about the seat switch, (especially if it can go in forward or reverse gear, without someone on the seat).