This problem has reared its ugly head again so i managed to borrow a set of connector tools to remove the pins (i dont know the proper terminology for the tool kit) which worked very well and i was able to remove the entire plug casing revealing access to all the individual wires right down to their crimp connection. i could also remove the pins individually from the internal connector block.
Upon gaining all this lovely access i plugged the wires back into the ECU with the main plug casing still removed, my hope being that i could fiddle with each individual wire with the engine running until i find the one with the problem. However, no matter how i manipulate the wires i could not then get the problem to re-occur.
thinking that one of the wires i pulled out and looked at must have not been seated correctly to start with i patted myself on the back and put the plug back together, cleared the error code and started her up!.....
Problem is now back! after alot of expletives i again pull the plug apart and reconnect without the main housing and again i cannot replicate the fault so i'm stumped and have left it as is but there is nothing to secure the pugs in place so they'll likely fall out soon.
I'm not a thick person and have always been quite good with this sort of thing but this has beaten me good and proper, i sat on the front cross member laughing at it in disbelief....
The only thing i can think of now is this: the mate i borrowed the tools from said 'when you find the break, make sure you use a crimp connection to fix it because solder will give a different resistance and may cause problems with the canbus signals' fine i thought, i will. thinking about it now, the replaced connector on the Cyl 1 injector has been soldered on so it could be that by fiddling with the ecu plug the canbus isn't happy depending on the resistance in the plug terminals which may compensate for the soldered plug if squeezed on tighter? i don't know.
i'm almost at the point now of paying an auto electrician to have a look. i suppose i should re-do the injector connector first.