I may have an answer for you. First I have to ask, is the chuff sound level lower than the whistle or bell? For example, when you run the locomotive the chuff sounds quieter than normal. If this is the case do this, turn the volume all the way down on your command controller. Next, when the volume is all the way down press and hold the aux-1 button, like you are activating sequence control. You will notice that you cannot turn the volume up all the way, but eventually it will come back up. Once the volume is back to it's full volume the locomotive should be back to it's original settings. If that is not the case then I got nothing, sorry.