Tailgate latch unlatches, will not stay locked

[Fortiswick]

Whilst reading through the forums there are plenty of posts about tailgate faults, but I cannot find a solution to this specific problem.

The power door works perfectly, except when it closes and latches, it has started immediately unlatching leaving the tailgate unlocked.

The sound I hear is of the latch closing then immediately opening again, this happens whether I close it manually or using the power door, I have tried slamming it shut hard, very hard!

This works sometimes but on a journey it will sometimes unlatch itself again.

I have meticulously checked to see if there are any obstructions preventing the tailgate from closing.

I removed the latch (leaving it connected to the electrics) and tested it by using the barrel of a screwdriver to simulate the catch, when I put it into the latch it closes around it as it should then cycles open.

The only way this stops happening is if I hold the metal actuator away from the lower micro switch whilst operating the latch (see pic with my thumb on it). I can feel it slip against something and then it rests away from the micro switch and the latch says closed.

 Unfortunately what is behind that actuator is sealed inside the plastic case which I don’t want to be break open for fear of causing unnecessary damage

 Has anyone had this fault and if so any fixes please?

I am tempted to get a new latch assembly and fit it, but if it the fault is generated elsewhere I will be throwing good money away on a part I don’t need.

 For now to make sure it doesn’t fly open while driving I secure it internally with a bungee.

 

This fault has two irritating side effects I need to mention

1.  Triggering occasional key detected in vehicle warnings, this not an issue as it seems to be caused by driving with the tailgate unlocked over bumps, the movement cause to latch to cycle ( latch-unlatch).

2. The constant audible door open alarm, is driving me crazy 😱 does anyone know of a way to silence the audible warning alarms?

 

 Thank you

[Herbie]

You can probably use Techstream to silence the alarm and while it's connected you could also look to see if any OBD2 codes have been generated.

[steve2006]

Having looked at the exploded diagram there are 2 “sensors” on either side of the tailgate, not sure what they do but may be worth checking there are no obstructions around them also.

[Herbie]

I think they're the crush sensors so that if the tailgate comes down on your hand or something, it reverses the direction of travel and lifts the gate back up again.

[Superduner]

It's a long shot, but check that the manual rubber covered switch is not being held in/jammed.  The cover on my switch had been "repaired" by a previous owner by painting it with what looked like underseal.

Over time, this had seeped into the actual switch and jammed it.

A new rubber cover from eBay was about a fiver.

It did however take well over an hour to clean out the switch and get it working properly again.

[Fortiswick]

Hi.

 Thanks for the suggestions.

 I'm not onboard with techstream yet, but it seems I need to be so I'll be sourcing it this weekend, my little OBD reader is not showing any faults.

I've checked the rubber over the boot  switch its OK, the onboard sensors don't seem to be playing a part in this either.

I started by emptying  the boot space and taking off the tailgate trim, so no obstructions, rogue bits of rubber or trapped debris anywhere.

 Before removing the latch I siliconed the struts (in case they were sticky)  and greased the working parts of the latch.

After removing and testing the latch assembly I refitted it, put the lining back on and shut the tailgate...of course it now works perfectly, but as we all know these things will always recur at the worse possible time.

 I have read an unlatching tailgate is an issue with some of the R series (usually first noticed when the key in car warning is flashed up), various fixes have been tried, from packing the rubber stoppers to bending arms on micro switches, which indicates there maybe several causes as a opposed to  single one, but in most cases a new latch assembly  seems to have solved it, I suspected a broken spring inside the sealed  black bit (its metal not plastic) which pulls the actuator away from the micro switch after it cycles shut, but no way to tell unless I break it open.

 So its wait for it to fail again, bite the bullet and fit a new latch and report back.

[Fortiswick]

6 months on now, and no reoccurrence 🤞

[Barry14UK]

Your efforts well worthwhile then!  Thanks for updating - useful to learn how resolved as others may well have similar problem at some point. 

[Illogan]

12 hours ago, Fortiswick said:

6 months on now, and no reoccurrence 🤞

Let's hope that's " put a lid on it " then!

Thanks for the update Mike

 

[Fortiswick]

Still good, no recurrences of the problem, so yes I think its cured.

 But having  written this, sods law dictates it will return this week🤣

[Bluemarlin]

Sometimes taking things apart and putting them back together is all that's needed.

If it does happen again, and you get it serviced by Lexus, you could always get them to look at it under the Relax warranty.