Every time I use the diagnostics, I have to look up the functions and pinout in the service manual so I drew up the diagram below to serve as a quick reference. Perhaps it may be useful to others:

http://users.tpg.com.au/acheson1/images/DIAGNOSE.JPG

On the carby TP models the setup is quite different, just 2 connections dangling from the firewall, one for ignition cut and the second for testing the fuel pump.