Brilliant - I went and did the same (Brn + Brn/yell wires) and it scrolls through the modes.
If you short the other two wires against the Brown in Trip 2 it will either increase or decrease the Km's (or miles if your that way inclined). A toggle switch would suit that little beastie for a cheap tripmaster.
Its off to the electronics shop now to see the nerds for another toggle and were done. I'll chuck up a pic when im done.