Things like this are difficult to diagnose remotely, but here are a few things to try.
1) Confirm your sound system is working OK by unplugging your TMCC Command Base and applying power to your loco in conventional mode. RailSounds should work fine -- if it doesn't, there's likely some internal short in your locomotive.
2) If RailSounds works in conventional as per the above, then the focus shifts to the LCRU1. These have a socketed microprocessor on the board, which can occasionally develop oxidation preventing it from working properly. Use a small flathead screwdriver to CAREFULLY pry up one end of the rectangular processor (it'll have a white label on it), and then do the same thing on the other end to remove it. If you have any contact cleaner handy, do a quick wipe of the pins and then re-insert the chip, taking care to be certain that it's oriented in the proper direction. Apply power to your loco and see if anything has changed.
TRW
