MTH GS4 AFT PS 2.0 Engine forgetting programming when powered down

What's the model number of the locomotive?

Battery is more than likely bad. Replace it with a new battery or a BCR.

20-3077-1 was the item number off of the box. Figured the battery was bad but wanted to be sure. Thanks for your reply!

Sure sounds like a dead weak battery.  Replace it with new and charged.  G

@ChicagoUP3976 posted:

20-3077-1 was the item number off of the box. Figured the battery was bad but wanted to be sure. Thanks for your reply!

You'll need the 9V style MTH batter or BCR for that application. It has a PS2 5V board.

I bet if you open it up there is a white battery inside. Those haven't been available in years.

@ChicagoUP3976 posted:

... every time I power down the layout, or the loco hits a dead spot on my track (need to clean the layout) the engine forgets its programming.

I'll bet that when you remove track power or loco hits dead-spot, the sounds stop quickly rather than playing 5 seconds (or so) of shutdown sounds?  That's a give-away it's very likely to be a battery issue.  What's not documented well is that the engine saves its programming at the end of the shutdown sound.  So if the shutdown sound sequence does not finish (because of weak or dead battery for example), the programming is not saved.  Lather, rinse, repeat.

In the rare situation where you absolutely, positively, MUST save the programming and you don't have a replacement battery, you can sometimes simply turn the volume control knob way down (conventional), or set the volume real low (command).  If you have a weak battery, there may be enough stored energy to run the shutdown sound sequence at low volume since it's the audio at 1-2 Watts of power that is the biggest draw on the battery during shutdown.  Anyway, this MIGHT get you to live another day so to speak while you wait for a replacement battery.

Thanks all for the information. I went to my local train shop and picked up a few BCR units for this engine, and a few others. Figured it was best to support the local train shops around here instead of ordering online anyway! Problem solved, the AFT GS4 is now running like a top.

A special thanks to @stan2004, thank you for such in-depth information! Really helped me get an understanding of how this engine, and a few others in my fleet, operate when the batteries are low!