Need Help With Bachmann GS4 Locomotive

[KisNap]

my nephew pulled out the two wires from the two wire connector in his Daylight Express DCC locomotive.  We ordered the replacement wire which I've soldered to the remaining wire that was in place, but I can't get the locomotive to respond.  At first my DCC controller was resetting making me believe I soldered them incorrectly, but even once I changed them the unit does not move even though my DCC controller is not resetting.  Is there something else I need to do?  I cannot get the light to work or the locomotive to move and it has never been changed form the standard 03 address.  Any help or documentation would be greatly appreciated

I also understand that the locomotive took a trip to a carpeted floor from a stool, but nothing seems broken.  I opened the tender where the DCC board is and all seems to be in tact.

[ACY]

It sounds like you may need to replace the decoder.

[James in FL]

It sounds like you may need to replace the decoder.

Before I spent money on a new decoder, I would first do some continuity checks with a multi-meter.
Do you have access to a multi-meter?
If not, buy one for the cost you would pay for that decoder.
Almost a necessity for troubleshooting in this hobby.

[tlong]

If the model doesn't make any strange noises when placed on powered DCC track and no decoder smoke is coming from the model try to see if you can go into DCC program mode and get a response from the decoder.  The programmer should give an error it can not talk to the decoder.

If nothing - perhaps still a wiring/connection issue - be sure you have track power and the locomotive is picking up DCC power. 
If all that still doesn't could be a toasted decoder, but try testing using a Decoder Test Stand if available. 

DC voltmeters doesn't measure DCC power correctly so you need a special device for that - but it you can use it with the locomotive at the workbench to test wire connectivity.

Beware that DCC wiring is not forgiving like DC.