The only new Kato locomotive I have is a Kobo model with Digitrax SoundFX decoder. From your description, the model you have evidentally has a function decoder that controls only the lights, and it is probably built into the dummy plug in the JST socket. Removing that plug will allow the motor control decoder to control the ditch lights, so make sure the decoder you select has the ditch light function. When you install the decoder, you'll probably have to also remove the other dummy plug; i.e., if you plug a decoder into the 8-pin socket, remove the JST dummy plug, and vice versa. The instructions should tell you this.
EDIT: I just went to the Kato USA web site and read the instructions. It very clearly states, "Remove the dummy plugs" when you install a decoder. That means to remove both plugs.
Can anyone tell me a little bit about the newer Kato locomotives (like the new Dash 9s or SD40-2s) and how the built-in DCC decoder works ? From reading the sheet in the box it appears the built-in decoder is used just for ditchlights and such. It has a standard 9 pin plug and a dummy plug. What are folks using for sound and motor control for these ? And when you remove the dummy plug and install a 9 pin decoder does it disable the built-in DCC ditchlight controller ?
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