Thanks David. Yes, I have several versions of circuit diagrams.

Yes, I checked one diode (as per jon@work) but will try the others too.

Thanks for suggestion, yes, I work through the tests and see if they are the same ECU pins.

I'm beginning to think that the ECU module may be faulty and will get a replacement anyway. Whilst I have a 4x4 ECU, it is marked 4x4 only and the compatibility roll pins either side are different to my 2wd version, I don;t think it is worth trying to use it even though it will probably tell me if the self-test is blown.

(Shame you are not just down the road from me!)

Richard.