I've got the inertial switch intervened message. I've had it a couple of times in the past. First time it was preceded by a discharged battery and just decided to fix itself after I was fiddling with the switch on the battery and the one under the seat. I never knew what was wrong. Second time, battery was fine but I had slid the passenger seat fully forward. I moved the switch under the passenger seat slightly and all was good (it was loose) This time I took the seat partly out so I could see properly. The inertial switch was again loose - it was getting caught by a wire under the seat which was dragging it out place when the seat was adjusted. It is now upright, ion place and not getting caught but still no change.
The switch on the battery does not seem to have popped out, at least pressing on it doesn't do anything. The earth points are both good. As you can see from the images, I have 12.7 volts before the switch but only 1.4 V after (key not in ignition) The third image shows there is a small voltage from the wire that leads to the box, not sure what this does!
Given that it is stuck on my drive and it is not time urgent, I'd like to try to trouble shoot this myself, with all your help
Are the voltages I'm seeing normal? Should there be 12V after the box?
If there should be 12V after the box/switch thing, can I test start the car by bypassing it or can I only test with a new box (I don't want to create new problems or error messages unnecessarily)
If it is normal and the problem lies in the switch under the seat, how can I test it? Again, is there a way of bypassing it or can it only be tested with a new switch?
However, could it be that the problem is elsewhere? before it happened this time, the battery discharged overnight down to nearly 3V. Does this sound like an ECU problem instead?
Many thanks in advance for any advice.
Edit: I've got a spare fully battery which I have tried as well but no change. Unless both batteries are duff I think it is something more complex.