Right this is becoming a pain in my ass
This is what I know.
Lighting circuit does not go to zero volts, it is constant positive feed linked to battery saver relay. Negative goes to about 0.5v(roughly) which explains why LEDs with no resistor fitted may stay on dimly.
Continuity check failed because there is always continuity, not enough to make the meter beep but does show a low value around 200 ohms:-(
C4 38 lighting sense is no good because when I did a continuity test my led interior lamp stayed dimly lit
So I have not found a distinct open or closed circuit when the doors are opened or closed.
There are those connections at the door ajar switches, BUT, there are 4 of them not anything I can find that can be used as 1 connection for them all collectively
You may be able to use 4 relays for the 4 ajar switches so they all work independently and not feedback to each other.
Alternatively you may be able to add 2 relays to the interior illumination connections at the Bcm connectors c2 22(front) and c2 27(rear).
I haven't added a relay to test them tho but given the negative varying logic I think a relay would be cleaner, I suppose a loading resistor might work but I think a relay would switch off quicker as the power fades out.
You can take relay positive from f72.
I have a relay and will give this a try if you want but it'll be Monday
If someone else can spot something I have missed them feel free to join in.
The problem isn't getting it to work but is in getting it to work for all latches, simply.
Most of the system is constant live connection and logical negative.
Also consider that the switches on the lights may affect the tracker trigger output, that is why I suggest relays at the front and rear interior illumination at c2.
Been scratching my head over this, I don't know if your tracker negative trigger has a threshold or if it just wants to be negative closed circuit.
If you want to do it simple then c3 pin 1 is for the drivers door only which you can simply plug your negative to and be done with it, only problem is that if someone breaks into any of the other doors and not the drivers door then the tracker won't work.
Thing is tho, for all intents and purposes i find it very unlikely that a thief would break into your van and drive it away without opening the drivers door at any point
Sorry I haven't made a very clear and simple way to do all doors with 1 wire but I have really thought about it
If I find out anything else I'll let you know, or if you want a copy of the worrying diagram pm me your email address.