RailKing Proto sound 2 steam engine takes off full speed?

If you mean that as soon as power is applied the engine starts moving, you have a motor lead shorted to the chassis frame.

If you can power the track and the engine doesn't move until you scroll the thumbwheel than you have an issue with tach signal.  You still should have direction control.  You can lower track voltage while testing so the engine doesn't leave the tracks.

Make sure tether is installed completely.  After that it may be bad tether, bad tach, bad Power Supply board, bad tach tape.   G

GGG, that happened to me when loco was locked in conventional forward.  It was going so fast I didn't have time to try if any sounds worked. A "conventional reset" cured it.  Worth a try.

You can try a reset but the engine should build up speed if it is just locked in a position.  A conventional reset is 1W and 5B.  You will need to have track voltage down around 10V.  I still think you might have a wire problem to the motor.  G

Jesse:  You have to power the track directly from the transformer.  No TIU or DCS signal anywhere.  Apply power to the track.  Since the loco will take off, be prepared to hold it by hand and don't apply more than about 10 volts.  Press whistle once and bell 5 times, at 1/2 second intervals, using the transformer buttons.  The loco should reply with 2 toots.  If not, try again.

Jesse,

   Is this a brand new engine or something you pick up used?

PCRR/Dave

JESSE,

   Hate to tell ya but a trip to GGG's masterful repair shop is probably going to be required for your engine.  However try to reset her a couple more times and see what happens.

PCRR/Dave