ArntyR

wow...thank you both, PScan and markvrs... 

I've included a pic of my SAIC Pektron input plugs. There's 4 m/plugs which tallies with markvrs pic

Sooo...I use the markvrs diag to find which m/plug has that colour combination of wires (2 lilacs and a brown), remove it and use + probe on each one of those pins in the m/plug (the darker lilac and the brown) one at a time, - probe to an earth, and see if twisting the driver door key/switch changes the voltage? (are the wire colours actually the same as on the  diagram?) 

 

Okay, assuming the voltages change, we'll have affirmation that the door switch is registering and that the EKA number signal gets to the scu...

Arrgh...what if they don't change - and (aargh) what to do next if they do change?