What if you have the engine in doppler mode and get busy and forget about the engine and it's left parked on the layout . The remote goes to sleep, This is the scenario at a open house last week.. After everyone left ,we noticed the engine had very week sounds so we tried a feature reset a number of times. no go. With 6 or 7 remotes I don't think we picked up the remote that the engine was last run with. After reading about early 5 volt system speakers going bad , I figured that was it. However the fix was to turn the doppler on and off again and sounds returned to normal... Why didn't a feature reset restore the sounds with a different remote? Weird!! I guess my point is... perhaps this is another thing to try when sounds go a muck.