XJ40 trunk locks are evil, and overcomplicated, with too much delicate stuff to fail. Like the door locks. So I gutted a junk yard unit to find the source(s) of my agony.

You can't remove the assy from the boot unless the release button will depress fully. Ain't that a bitch if it's failed in the locked position. More on that in a moment.

Here's the backside of the assy:


4 wires controlling 2 separate demons. And the lever that pulls the latch release up by the button, if it's moving.

Yellow is the microswitch that, when open, via key, DISables the electric solenoid, rendering the glove box release button disabled. Purple and pink go to this fragile little heart of darkness not suitable for a cheap chinese child's toy, let alone a high traffic trunk latch.



This little tiny electric motor with plastic gear is smaller than the tip of your thumb.

The tiny electric motor is controlled by the central locking system and moves a metal lever back and forth to enable/disable the button that rotates the lever up to pop the trunk open.

 

Continued. (Hit the wrong key)



Metal lock blocking the button from pushing up. (Where my trunk spent most of it's 2 years whilst I fought with it...)

I finally figured out you can force the metal lock to the open position with a small screwdriver from the inside of the trunk. Took a while and the neighbors thinks I'm homeless and literally living in my trunk, sigh....



Now you can pop the trunk. Shouldn't the bloody key be able to move the lock to here?

You have to carve this assy apart essentially destroying it, unless you glue it back together and then you're never getting it open again. So, my key does not move this lock to the open position. Why? Dunno. Can't figure out how to get the cylinder out without destroying the assy.

What to do with this intel? Once you finally get into the trunk via the solenoid, you use your small screwdriver, from the inside, to move the button lock to the open position. Now your trunk latch release works again, but it's not secure, a canundrum no doubt. I had to unplug the tiny electric motor to make sure it wouldn't lock me out again if it decided to work intermittantly, which seems to be the case.
Back to the yellow wires to the microswitch. You turn the key CW and it opens the microswitch, disabling the glove box button. So, unplug the harness and jumper the body side yellow wires to eliminate the microswitch from locking you out electrically. As long as the junkyard trunk solenoid lives, you can glovebox button into the trunk.

So what am I left with? The key does not move the lock open but the electric motor will randomly move it to the locked position. I'm at the mercy of the solenoid not dying if I lock the trunk release latch. You can't get into the trunk any other way. Shall I install bailing wire through the lower license plate hole that will manually yank the latch release lever, hidden behind the license plate for emergency? It's a real love/hate relationship with Madame EMP, and the rainy season has begun in the North American rain forest. More on that later.

 

Thanks for the write up! I actually just posted about my trunk lock so its awesome to see it out of the car.

Question for you, do you have photos of how you took it out and ultimately apart? I cant seem to figure that out and since mine is still working and just making noise, I would like to see if I can restore it.

Thanks in advance!

 

Hey, I got this issue 2 years ago and I fixed it in quite drastic way.
What is surprising me is how the hell you were able to move this metal lock moved (by tiny screwdriver) so the button can be pushed.
You were able to do it when the whole lock was still installed in the trunk?
So you first opened the trunk in any "emergency" way, and then played with this having the lock still in place?

I had an issue that it was impossible to get it out from the trunk if the button is not pushed. And I could not push the button because it was blocked by this metal lock.

 

I've been in there too for mine. It seems like I used a pair of needle nose pliers or possibly small channel locks once I had the connector rod off of that arm. I do recall it taking some persuasion. You're probably aware of the very sharp edges too..

 

Maniak, true that the assy is not removable from the boot sheet metal until that damn button depresses all the way. I had to sit inside the trunk with the gutted junkyard lock in one hand, headlamp on my forehead, and "pick" the release open from the back side with the tiny screwdriver I use to set amp gains. See the 1st photo in post #2 to observe "below" the purple wire is where you can pry the lock open levering the screwdriver against the lock cylinder (not present in photo)
Once the button would depress, it was still a wrestling match to get it out of the trunk lid. Then I jumpered the little electric motor both polarity ways to the battery and could only get it to activate to closed/locked but not activate towards open/unlocked. Briefly thought about sourcing replacement motors but immediately barfed on the number of hours that project implies. Also discovered the key fob triggers that motor, haven't plugged it back in since. Would love to replace the entire "cental locking" philosophy with individual actuators and switches.