Hey all, wondering if any of you have encountered similar issue with the trunk light, it turns on when the boot is initially opened, but when it's 3/4 open the light turns off. Any idea how I can diagnose this issue?

 

Welcome to the forum!

When you open the trunk there is a switch in the latch (that's in the trunk lid) that tells the Main Body ECU the trunk is open.
The Main Body ECU then grounds the wire for the trunk courtesy light...as the light always has power.

I'd probably start with the easiest thing first and replace the bulb. Its probably a peanut bulb...it's definitely not an LED.
The Courtesy switch signal is independent of how much the trunk is open...it's either open or close, the amount of opening is irrelevant, it could be open 1mm and the trunk light should be on.

Has any work been done to the trunk of the vehicle? Like an accident of some kind.
Just thinking if the latch or trunk harness may have gotten damaged.
If the light goes out at the same exact spot of opening every single time (I mean the exact spot), then I would think it's a wire issue in the trunk harness...that when it gets to a point the wire for the switch in the latch goes open circuit, so the ECU thinks the trunk is closed.

 

Definitely not the bulb, as I've tried changing it. You are right, the car actually doesn't recognize that the trunk it's open when it's fully opened, only when it's half-way opened I see the warning on the dash.

No accident at all, but it does seem like it is a wiring issue in the trunk harness, the light turns on from the moment the trunk is opened until halfway through and then turns off.

 

Based on the fact the dash light is going out when you pass half way then I think you are looking at a wire issue.
The switch in the trunk latch is normally open when the trunk is closed...so when the trunk opens the switch closes, telling the ECU the trunk is open.
However, if the wire is broken somewhere, as you open the trunk and the wire goes open circuit, then the ECU thinks you just closed the trunk, as that's the equivalent of the switch being open circuit, when the trunk is closed.

The most likely place the wire is broken is at the hinge. I believe the trunk lid harness is on the left hinge, so that's the first place to look.
Maybe the harness closed against something in the trunk one time and it damaged the harness...or the trunk could have been opened and closed more than an average amount of time during it's life.
Either way you have to open the harness and find the wire to repair it.
The wire is Green, which doesn't mean much cause there are probably several Green wires...but the casing of the wire likely has a crease, which would indicate the copper strands inside are broken.