For all the installations I do with the CC-M, I have never needed pin 2 of the 10-pin connector. I did fool around with it once to see what happened, but it doesn't actually output usable serial data, not sure what it's outputting.
The top suspect for taking off is that pin 1 of the CC-M 10-pin connector isn't connected to pin-24 of the R2LC (serial data). Also, if you didn't get the newer CC-M labeled Diesel and Steam, you may have a problem driving the wireless tether and the CC-M, the serial data isn't strong enough to drive both of them with the older CC-M versions. I had to add a serial data buffer to some installations with the older CC-M to solve this issue.
In this diagram, RailSounds Serial Data In goes to the IR tether or the RailSounds board in a diesel installation.
