Lionel K4 with smoking whistle does not work, cab light flashes four times

You have two problems.  If the tender sounds work under command control, the tender coupler has nothing to do with the whistle steam not working.

The blinking code 4 is for the whistle steam heater fault.  Lionel was too generous with the cut-n-paste and left out the diagnostics for the second smoke unit.

I suspect clearing that code will require taking the locomotive apart to see why it has an issue with the aux smoke unit.

@gunrunnerjohn posted:

You have two problems.  If the tender sounds work under command control, the tender coupler has nothing to do with the whistle steam not working.

The blinking code 4 is for the whistle steam heater fault.  Lionel was too generous with the cut-n-paste and left out the diagnostics for the second smoke unit.

I suspect clearing that code will require taking the locomotive apart to see why it has an issue with the aux smoke unit.

The railsounds does work as intended under legacy. I am guessing the coupler doesn't fire because there a bad/cold solder joint or a broken wire to the coil. Ill take a look when I take the shell off, but before I do, i wanted to ask the forum for questions. Thanks again!