I've just checked the wiring diagram . The wiring for the diagnostics plug have a connection on an ' adapter plate ' which is located on a bracket above the relay plate/fuse box .
This is where you should find the two wires that go to the ECU , one is Yellow ( 0.5 wire size ) the other is Grey with a white tracer ( also 0.5 wire size ) .
The positive feed comes from fuse 21 ( 15 Amp ) then the Q/5 connection on the back of the relay plate via ( dash panel wiring loom) Red with a white tracer ( 1.5 wire size )
The earth wire is Brown ( 0.5 wire size ) and is connected into the wiring loom for the instruments .
    ÂÂÂ
Hope this helps,
Oli :smiley:ÂÂÂ