Reseting HO athearn genesis GP9 to factory settings for DCC?

[p51]

A neighbor has an HO athearn genesis GP9.
He says with DC, it'll run. I don't have a DC throttle to test that.
In DCC, you can do all the sounds and when you crank the throttle, it makes the sounds of running, but it won't move. Not at all.
I have an MRC prodigy express DCC and I looked up any codes to reset this thing back to a factory setting so he can run it in DCC.
 Nothing works so far.
Any clue someone can give would be appreciated, I owe this guy more than one big favor (saying he's helping me with my WW2 jeep would be wrong as he's doing most of the work so far) and I'd love to hand it back running in DCC.
Has anyone encountered this?

[peteski]

What brand/model is the decoder?  Any history of the failure?  Did it run for him in the past, or is it a new to him model?

For DC test you could try using a fresh 9V battery. Touch the terminals directly to the wheels. A standard alkaline battery (not a rechargeable one  which provides less than 9V).  It might not be enough to get the sound decoder to run the motor, but it is worth a try.

Or if you have cordless drill or other tool using 12V battery pack, you could take some test leads (if you have them) and connect the battery terminals to the wheels wipers or track pickup wires in the loco.

Can you verify positive connectivity of the motor leads between the motor and decoder? Again, if it runs in DC then the connections are ok.