Traderal; On the left of my dash and down is a row of 6 switches (gen start, fog lights, air dump, etc.) with the diagnostic button the 6th from the left.
I push and hold, turn ignition to on(not starting), all lights will do there normal check and go out. If the warning and stop engine lights return and stay lit then there are no codes to read. If they start blinking, the warning lite will stay lit and the stop engine light will blink the code (four blinks a short pause three blinks a short pause four blinks a long pause repeat 434). There are some rigs that using the accelerator some way will do the same thing.
2005 BTCruiser 2750 always
2005 Tracker 4X4 usually