I'm not Bach-man, of course, but I was curious. It's odd that there's no wiring diagram in the Climax drawings. But, the K-27 drawings have pinouts for J1 and J2, and the functions you mention line up. If it's indeed the same, the rear light is J1-9. Here's the K-27 drawing:
https://www.bachmanntrains.com/home-usa/dwg/dwgs/83093.pdf
https://www.bachmanntrains.com/home-usa/dwg/dwgs/83093.pdf