MTH Proto2 Diesel

It may be tough to do but try a conventional factory reset with the horn/ bell combination. Better yet find someone with full dcs and do a feature or factory reset..  

 Since the engine will move from forward the battery must be good, Most of the non-working items may be on the  the 12 pin wiring harness.. Maybe try reseating it. (pull and put back in) Good luck.

There will  more help shortly...from other DCS guys.   

Going to the control systems forum under the DCS section and asking this question there might get you more help, and I hope you find a good resolution, these situations are so frustrating!!!!    Good Luck      

cTr...( Choose the Right )

speaker magnet metal crusty?

For a PS-2 5V board with no sounds and everything else working you have a few issues to look at.  First did it work before changing battery?

Check volume pot for operation (required for conventional operations. CHeck for bad speaker, check for wires coming off volume pot or speaker.  Do a conventional reset, or test in DCS and feature reset.

After that, may be a bad audio amp.  That can be tested and repaired at component level.  My e-mail is in my profile.  G