As some have noted, there is no switch to turn on all the interior lights on newer TCs. This modification will allow you to turn them on with a separate switch. Opening a door turns on all the lights, so I added a switch that activates the same circuit. You can easily turn on the lights and the van thinks you have opened the driver's door. It works well and the only hitch is you get a "door ajar" message on the message center.
This is not a complete step by step but it covers the tricky parts.
The most difficult thing will be removing the door panel without breaking any tabs or pins. You should have a panel removal tool (or tools). There are dozens on Amazon for under $20. You may also want to buy some spare clips for the door panels. Several are tough to reach even with the tool and you may break one
Remove the plastic cover behind the door handle. It pulls straight out. Pry at the spot noted to avoid breaking any tabs.
Remove the small panel behind the door latch
Remove the door panel and unlatch the door handle
Here is the wiring diagram. I used a pushbutton switch. This type of switch needs to be latching. You can use a rocker or toggle switch that has a normally closed terminal. The switch will be normally closed and open when the lights are turned on. The lights go off when the switch goes back to closed. I also used a lighted switch so I had to connect power for the light. The light is not necessary so only do it if you like the look.
***see diagram below***
Here is the power for the lighted switch. It is tied to the light for the door lock buttons. I used posi-lock connectors for this connection.
The switch is wired to the door module. Pin 14 is cut and the switch is inserted. Here is the door module with the wire already cut. The wire had green paint on a black wire.
Another view of the cut wiring
I wired the switch using a modular pigtail that plugs in (for door panel removal in the future). These connections were soldered. The wire was dressed with Tesa cloth tape (I love this stuff). The Tesa tape prevents rattles and will not get gooey with age like some electrical tape.
The finished product. The switch light is always on just like the lights on the door switches. But I can't see it from the driver's seat (hence the uselessness of the light).
You will get the alarm chime and message when you turn on the lights, but they work fine (just like opening a door while driving). Of course I insulated the door panel with theromozite and it gives the door a solid feel and dampens road noise. Insulating takes less than 1 hr per door and I highly recommend it. Use spay on adhesive to apply.