Thanks big bob, with what you said about the pwr,gnd,ibus, I should be able to quickly verify the tcu is good or not. -Which'll be great start.

Just quickly, what is the retrofit cable for? (I don't think I've done enough research yet to 'click' about what you're referring to?)
Does it run between the radio and the 54pin plug I'm getting for the tcu. Or do I plug it between the radio and something else in the car?

'cheers
Sim.