So after a bit of research I was able to fix my rear dome light problem. What was happening was the "Door" function of the light wasn't working when I opened the lift gate. It would work fine when switched to the "on" position though. The first thing I did was check the wiring harness between the door and the body for the common broken and cut wires. Sure enough, two of the wires had their insulation cut or split open as seen here:



However, even though I fixed the cuts, my problem still persisted. So I started looking for the door switch by taking off the covers and panels to expose the internals of the lift gate.



After hunting around for a bit, I found that the door switch is internally part of the latching mechanism. If you look directly to the right of the coil spring you can see the latch cable and also the switch wire. I disconnected the connector that goes to the switch and jumped the source side of the connector and was able to confirm that this was indeed the right wire as the dome light on the "Door" position came on. I also checked the switch side for continuity and found that the circuit never changed state with the latch closed or open so there is obviously a problem in the switch.

I removed the 3 - 10 mm bolts that connects the latch and let it drop down for access as seen here:



I pulled back the rubber cover on the back of the latch (missing from the picture) and liberally sprayed some degreaser into the latch to get the old grease and grime out of it and worked it really good, opening and closing the latch for a few minutes and reconnected the plug. I can't believe how much dirt and crud came out of there but at any rate the light works great now! I'm not going to spray any kind of lubricant in there at this time as I want to give it some time to see if it's really needed.

So the bottom line is, if you are experiencing the same issues with your Rear Dome light then 1st, check the wires between the door and the body then 2nd, clean out the latching mechanism. That's it!

 

thanks for posting this up and the excellent pictures. I finally got around to this after putting up with it for several years.

Same thing with mine, I removed the latch mechanism from the hatch body and sprayed degreaser in there liberally and voila! all seems well now.

 

Glad it worked for you.

 

UPDATE: The same problem happened again but this time it turned out to be a broken wire on the lock assembly as you can see in the picture. Not much I can do about this due to it's location so looks like I gotta bite the bullet and order a new one

 

Glad I found this thread, mine has been intermittent for almost a decade so I just leave it off. I will trouble shoot this in the summer. Thanks...