Originally Posted by big_wasa

I can't comment on the Boa or Bob as I've never done one but I have done a lot of other Ford ecu's inc most of the zetec's inc the Focus Rs mk1 and some of the Duratec's inc the st220 v6.

The ecu itself would normally have one permanent live ( orange or red ) for the memory and two switched live's.( green/ yellow ).
There would be 3~5 chassis earths ( black/ yellow)

The brown sensor earths are balanced and would all connect to the one pin from the ecu not the chassis earth.