I have done a search on this topic and have encountered a lot of people who do not have a functioning trunk light nor rear dome light in their sedans. No one has posted an answer as to how they solved the problem. Someone suggested peeling back the rubber sleeves at the rear door hinges to check for broken wires. I looked at the sleeves of both rear doors since they didn't specify which rear door. I moved the wiring harness up and down hoping to get an intermittent connection - nothing.

Occasionally the trunk light would glow dimly, that no longer happens. A dim glow would suggest a bad ground. I checked all the grounding points, in the trunk itself, the sockets to the taillights, the ground location under the gear selector. Does anyone have any idea what is happening with this?

__________________
Remember, Bad Decisions Make For Good Stories

C'mon, anyone? I'm dyin' here...

__________________
Remember, Bad Decisions Make For Good Stories

I don't know anything specific about your car.... But speaking in general, dome lights on many cars are switched by a body controller computer. This allows other situations to activate the lights, like using the remote to unlock the car. It allows for slow dimming of the lights instead of hard on-off cycles. It keeps the lights on for a while after you lock up. And the door and trunk switches may also serve as triggers for the alarm system. In short, it's more complicated than just closing a switch to ground which carries all the current for the lamps like on old cars. You need to get an electrical diagram. Then a systimatic trouble shooting aproach should guide you to a fix.

__________________
Resistance is Futile.

The rear trunk lamp is also shared by the antenna motor - it was one fuse in the fuse box that blew and caused the trunk light not to function.

Check for voltage at the connector.

your car does not employ a body control module for the rear or front dome lamp, infact the only module it has is a convenience module which works to self close the windows when the doors are locked with the key.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Interesting - thanks. I scrutinized the wiring diagram and found that the rear dome light does wire into the convenience module. I haven't found out which part of the module though (A,B,C etc.). This is annoying. The rear dome light also gets power from the driver's rear door puddle light. The red/white wires on both lights have continuity. Only the puddle lights work with the door opened or with the use of the rocker switch on the dashboard. It's as if the bulb is completely burnt out - which it's not.

The trunk light will extinguish if any of the doors are opened, then it will relight when the doors are closed (all while the trunk lid is open of course). I'm trying to find a common thread/module/wire that these two share. I thought it was the CCM, I'm still not convinced.

__________________
Remember, Bad Decisions Make For Good Stories

quite spooky behaviour

in my car the rear dome is lit (along with rear puddle lights) by either opening either rear door or the rocker switch on the centre console.

The trunk light does nothing with doors, only operates with the trunk lid switch.

I once blew out a fuse that was for the antenna motor, it caused both lamps you mention not to work.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)