Just a couple of questions..
When you say 'disconnect' the CU, what do you mean please?
You are talking about the 'airbag' CU and not another CU are you? Is not, where can I find that one? Secondly, if the Airbag CU was faulty or not working at all, wouldn't that be flagged up by the diagnostics tools? And in that case we are talking about the main CU? Any idea where the fault codes are stored? I presumed it wasn't in the Airbag CU but the main CU if there is two on the car or am I mistaken and there is only one that is under the centre console at the rear?
I have got a multimeter but not the other which I can rig up.
I would disconnect the battery before removing any equipment including the airbag CU but will need it left in position to check the voltages anyway.
Is the K bus comm unit part of the Airbag CU or somewhere else? Sorry for me being dim.
Kind Regards and thanks