Loss of rail sounds in Legacy GP9 diesel

Have you tried it conventionally with the base unplugged?

Yes, still no railsounds.

Referring to the link in the original post, I was wondering if there is a different reset code for this engine (other than "2").

I found that if I address the GP9 using the universal ID, 99, railsounds work.  I will contact Lionel support and ask if there's a special reset procedure for this engine.

I am perplexed by this. If the sounds work when addressing the engine as 99, there's no reason they shouldn't work when sending commands to that engine's unique TMCC ID.

The normal reset command is to send the engine the <0> key or the reset button. See page 16 of your locomotive's manual: 

https://www.lionelsupport.com/...4662250LEGACYGP9.pdf

Do you have the capability to make a little video to post here? Perhaps that would help clarify the problem. If you do, please point the camera at the CAB Remote, we will be able to hear what the engine is (or isn't) doing from the sound alone, seeing a video of the train doesn't add much--but a clear view of the buttons you are pressing on the CAB might tell us something. When the sounds fail to play, please confirm that motion, couplers, etc continue to operate as expected.

CORRECTION: The GP-9 sounds do not work when addressing the engine as 99. While preparing for the suggested video, I discovered that I apparently confused sounds from another engine as coming from the GP9. The normal reset commands have no effect, so I suppose I have an electronic problem that will need repair.

Railsounds and others, thanks for your attention. I apologize for the misinformation and confusion.