Hi SimonThanks for the info. We have today back probed the ECU whilst cranking to see what sort of power was getting to the ECU.
Pin 13 VBat drops 700mv with Ign on and 900mv whilst cranking.
Pin 35 VBat drops 12mv with Ign on and 90mv whilst cranking.
Pin 36 Gnd drops 12mv with Ign on and 160mv whilst cranking.
Pin 54 VBat drops 14mv with Ign on and 170mv whilst cranking.
VBat was dropping to 10.8V on cranking.
I don't think any of the above seem excessive. Note that pin 13 is fed through a diode in the main relay which will account for 600mv.
There is an transponder immobilizer fitted to this vehicle and we are hoping to get hold of another key. So it could still be an immobilizer fault or possible ECU fault as you mentioned.
I also need to check out the wiring to the diagnostic connector to see if there is a problem there as to why it won't talk comms.
I know you can only reprogram the immobilizer with the right tool but I wonder if it has it's own serial line or whether it goes through the ECU.
I think we may be hiring a replacement ECU as the next step.
Many thanks
Sean.