Boot won't open on unlock only on middle boot switch

[lfcmassive]

Hi guys new to the forum so hello I have a problem with my boot when I unlock the vehicle the boot will not unlock. but when I push the middle button ie boot unlock icon the boot will unlock. I have tested the switch and it is fine has anyone else had the same problem at all....

 

Regards Dan.

[ords]

 

[ApertureS]

What switch have you tested and how do you know it’s working?

 

if you’re talking about the tailgate external boot handle/button. There is a 99% chance that this is faulty so I’m not sure how you could have tested it?

 

If you’re in the U.K. I sell genuine used boot handles for £25 posted.

[daftbugga]

Hi Dan 

Welcome to the forum .

Does pressing the unlock button unlock all doors but not the boot ?..
Or does it unlock drivers door only ?..
If it unlocks drivers door only with a single press try pressing the unlock button twice in quick succession.  The way it acts can be altered in the menu , I cant remember what setting its called ..
Sorry if that's taken as teaching grandma to suck eggs .. 

[lfcmassive]

I tested it with a multimeter. pressing the unlock. unlocks all the doors but not the boot. only unlocks boot of middle boot button 

[ApertureS]

13 hours ago, lfcmassive said:

I tested it with a multimeter. pressing the unlock. unlocks all the doors but not the boot. only unlocks boot of middle boot button 

Please be more specific, what have you tested with a multimeter, how have you tested it, what is the values of the test?

 

The way this system work is there is no 'unlock/lock' for the boot. There is simply 2 boot latching releasing methods - the key fob middle button that works all the time, and the external boot handle when pressed sends a 12v signal to the BCM, this then checks if the car is in a locked or unlocked state, if its in an unlocked state, it sends 12v to the boot latch to release it.

 

So if the key fob is releasing the boot latch, then the boot latch and wiring to it is working no problem. The only part that is going to be faulty is the wiring to the external boot button or the external boot button itself. Thats why im a bit confused when you say youve tested it but wont say how or what the outcome is. 

Edited 17 December, 2023 by ApertureS

[Breezy_Pete]

11 minutes ago, ApertureS said:

the external boot handle when pressed sends a 12v signal to the BCM, this then checks if the car is in a locked or unlocked state, if its in an unlocked state, it sends 12v to the boot latch to release it.

Or to put it another way, when the button is pressed it earths a 12V signal from the BCM, a 12V that won't be there if the BCM is asleep cos the car is locked. 👍

[ApertureS]

20 minutes ago, Breezy_Pete said:

Or to put it another way, when the button is pressed it earths a 12V signal from the BCM, a 12V that won't be there if the BCM is asleep cos the car is locked. 👍

The BCM is awake even when the car is locked 😛 Stays awake through most things as it is the controller for the central locking, if it was asleep, you wouldnt be able to unlock the car.

 

[Breezy_Pete]

Fair enough but I'm right about the earthing, right. 

[lfcmassive]

what will it be under in VCDS to check for faults 

[PetrolDave]

Just now, lfcmassive said:

what will it be under in VCDS to check for faults 

Do a complete Auto-Scan, you should see errors under 09 Cent. Elect.

[ApertureS]

5 hours ago, lfcmassive said:

what will it be under in VCDS to check for faults 

09 for bcm

6d for electric tailgste

 

although a faulty boot switch won’t give a fault - it will just think you aren’t pressing it.

[Dooge]

For the sake of £25 I'd just get it done. Its unlikely to be anything else if it works from the key fob and they are a common problem. Easy to change over as well, the harder bit is getting the large plastic panel back on.

Edited 29 December, 2023 by Dooge

[lfcmassive]

I have bought another that does not work either 

[PetrolDave]

1 hour ago, lfcmassive said:

I have bought another that does not work either 

Could be a wiring problem, most likely where the wiring passes into the tailgate?

[lfcmassive]

What’s part number for this part 

[lfcmassive]

sorted it was the main locking mechanism