Still no ETIS but I've done some work on this. Maybe you can compare your readings to mine. Mine is UK RHD so my locks may on different side if yours is a different model.
I started this with an unlocked van which had been sat for an hour or two. No interior lights were on. I didn't put key in ignition at any point.
All lights off.
1. Open O/S rear door, interior lights on
2. Close O/S rear door, interior lights off after 10s
3. Open side door, no interior lights come on
4. Close side door, no interior lights come on
5. Open O/S rear door and side door, interior lights on
6. Lights will not go off until all rear doors closed (even though the side door didn't bring them on in 3)
7. Lights stayed on for at least 5 mins at which point I moved on and closed all doors, lights go off
Locking - After opening a door...
5. If ANY door is open, if I try to lock van, it sounds horn, doesn't lock and keeps interior lights on
6. Front doors closed. If side door or O/S R/H barn door is open, it sounds horn, doesn't lock and keeps rear interior lights on
7. The N/S barn door has two catches one at the top and one at the bottom. These have no electrical input to the system. You can leave the door open, as long as you close the O/S door and still lock the van with the door wide open. Interior lights go off. I tested the two catches individually by moving each locking mechanism closed with a screwdriver. They do not affect locking or interior lights.
Simulate door closed...
8. Now for the next bit, instead of opening and closing doors I simulate them closed by moving the locking mechanism with a screwdriver. This is reversible when you pull the door handle and can move them back.
9. Open O/S barn door, simulate door closed by moving locking mechanism. Interior lights go off and can "lock" van
10. Unlock van, lights come on and go off after 20 seconds
11. Pull handle and move locking mechanism back, interior lights come on. They stay on for at least 5 mins.
12. The side door is tricker. Mine has 3 spring loaded metal contacts which connect to 3 metal contacts on the B frame. This contact assembly is attached with a couple of security screws. I don't even have a bit for them in my kit, (yet
. Suspecting there could be some kind of control circuit in this assembly or at the door lock at rear of door and without a wiring diagram yet, instead I measure the resistance between the pins:
Pin 1 is highest, 2 middle, 3 bottom.
Pins 1,2,3 to vehicle earth - open circuit infinite resistance
Pin 1-2 12 ohm
Pin 2-3 15 ohm
Pin 1-3 26 ohm
These do not seem to change when the spring loaded contacts are pushed back
(It would be worth checking yours are the same if not could indicate damaged door lock circuit in the assembly)
Without removing it, I can't be sure exactly what components are inside this assembly but I bet the BCM uses it so your resistances should be similar. To simulate this device, I could try hanging in similar resistors across the b-frame contacts although I imagine there is more going on than just a few resistors. OR it could simply be a slightly high resistance due to the way the spring contacts are electrically connected, similar to a slip ring.
13. Simulate side door closed by manipulating locking mechanism at rear of door. Van will not lock and does horn thing with lights still on UNTIL I bring the door back forwards so the spring contacts are mated. Van then locks and interior lights go off (but door is not fully closed). Measure spring contacts resistances again but same as before.
14. Don't panic if you can't move the locking mechanism back. It will still be locked, even if you press unlock on the remote. You need to make the spring contacts mate again to unlock it, then you can pull handle and release lock then close door again
15. Even if I simulate side door closed and then lock it (with contacts closed) and then quickly open the door again so the spring contacts are not made. The light interior lights stay on until I bring the door back again and the spring contacts are made. You have to do this within the 5 second timeout or they will go out. Opening the door after this does not bring them back (because my side door does not bring lights on as in step 3 above)
Hopefully, your van also does the locking horn thing. This should at least tell you if your door lock contacts and the spring contacts are working. Only problem is the side door is going to make this more difficult to pinpoint at the moment without the wiring diagram and as there's no difference in resistance at the spring contacts when side door catch is in either position.