Hello everyone,
I am no auto sparks or mechanic. Just trying on a best endeavours basis here....

I've been working through a battery drain, with a multimeter in series on the negative terminal, and pulling fuses one by one and noting the change in the drain.

I suspected it was the BCM staying awake, if I pull that fuse the drain drops. However, if I leave that BCM fuse in place and leave the car for an hour and the drain was still the same, nearly 3 amps. So I went through every fuse to see if I could find an additional drain that would indicate an active system which might be keeping the BCM awake.

However....

This is by no means conclusive at the moment, but I suspect that the cover on the diagnostic port (by the drivers right knee on a RH drive vehicle) is a significant contributor.

Yesterday I found that if I close the cover of the port then my drain is 2.6 amps. If I open the cover the drain drops to 0.9amps. I found this after pulling the fuse that is for the diagnostic circuit yesterday. The fuse is for a few things, IIRC interior illumination, diagnostics, and one other thing.

I had read on this webpage below about a similar issue, and that is what gave me the clue to try removing the cover:
https://www.justanswer.com/uk-car/23bkd-ra...t-two.html

Has anyone else seen this or can anyone offer any supporting information, tidbits of useful info?

If not, then hopefully this will help others when searching for a battery drain - check your diagnostic cover.

Thanks
Mark