GGG, you're not the only one who is confused. The parts diagram for the 30-1164-1 RailKing Mikado does not show any marker lights, other than what is illuminated indirectly by the headlight bulb. The LMK softkey turns LED markers on and off, but this engine does not have LED markers, which means that the LMK softkey on a 30-1164-1 would be turning a circuit on and off that has nothing connected to it. This would explain why it's not working.
There is an incandescent bulb that illuminates the Markers indirectly. There is a senate bulb for the headlight on the shell. They are two different bulbs. I used to be able to turn it on and off with the LMK softkey prior to the original 5v board dying. When I had a tech upgrade it to 3v, they could not get the Marker bulb to work. Hence, I swapped the board with a diesel I have and now the bulb works, but I cannot control it with LMK like I used to. If you’re familiar with the ADPCM program, it allows you to change the soft keys for a sound file. The default for the Mikado’s file is listed as “Marker light on ditch”
I added some pictures for clarity. Note how the headlight and marker bulb are indeed separate. Also note the use of the 8 pin connector for the marker bulb.
