Rear door not locking

MikeS100 · May 8th, 2019, 20:58

Hi all,

My XC90 has an issue with the rear passenger door not locking. Sometimes it does lock correctly on the 1st attempt, if not then it always seems to lock on the 2nd attempt. So I press the lock button and 3 doors lock and the lights flash. Press unlock and they unlock as expected and the lights flash. Press lock again and all 4 doors lock and the lights flash.

When driving, if autolock is on then sometimes all 4 doors lock, other times it's only 3. If autolock is off then it seems like all 4 doors lock when pushing the button on the drivers door. At least they did when pushing the button today.

It's only an issue with locking, it always unlocks fine.

I have tried two methods I have read to reset the UEM but neither way made any difference. The first was key in ignition setting 2, hold driver and passenger window buttons up for 5-8 seconds, release buttons, remove key, lock and unlock on remote twice. The second method was lock and unlock the car using the key 3 times in a row. There was nothing to confirm whether it did reset or not. Any other ways to reset the UEM?

Any ideas what could be causing this? It feels like it's electrical but is it worth changing the door lock? Is that a big job?

Thanks

SwissXC90 · May 9th, 2019, 07:05

It'll be one of the folloiwng:

Sticky mechanicals inside the actual door lock
Failing microswitch inside the door lock
Broken wires in the flexible wiring loom between car body and door

To diagnose do this:

Take off the door panel and inspect the mechanicals, see if you can find anything sticking and not moving freely.
Measure the lock/unlock signals with an oscilloscope and look for noisy signals indicating poor microswitch contact. If so, replace lock mechanism (as switch is buried deep inside the lock)
Wiggle the door cable while an assistant locks and unlocks the car, see if you can reproduce the problem to determine if a wire is broken

MikeS100 · May 9th, 2019, 08:21

Thanks SwissXC90. I dont have access to an oscilloscope but I can try with an assistant wiggling the wires. If it's not the wires then I guess I will try swapping the lock

May 8th, 2019, 20:58	#1
MikeS100 Premier Member Last Online: Mar 21st, 2024 21:39 Join Date: Oct 2011 Location: Sevenoaks	Rear door not locking Hi all, My XC90 has an issue with the rear passenger door not locking. Sometimes it does lock correctly on the 1st attempt, if not then it always seems to lock on the 2nd attempt. So I press the lock button and 3 doors lock and the lights flash. Press unlock and they unlock as expected and the lights flash. Press lock again and all 4 doors lock and the lights flash. When driving, if autolock is on then sometimes all 4 doors lock, other times it's only 3. If autolock is off then it seems like all 4 doors lock when pushing the button on the drivers door. At least they did when pushing the button today. It's only an issue with locking, it always unlocks fine. I have tried two methods I have read to reset the UEM but neither way made any difference. The first was key in ignition setting 2, hold driver and passenger window buttons up for 5-8 seconds, release buttons, remove key, lock and unlock on remote twice. The second method was lock and unlock the car using the key 3 times in a row. There was nothing to confirm whether it did reset or not. Any other ways to reset the UEM? Any ideas what could be causing this? It feels like it's electrical but is it worth changing the door lock? Is that a big job? Thanks __________________ 1999 V70 TDi (auto) 2002 C70 T5 GT Convertible (manual) 2008 XC90 D5 Executive (auto)

May 9th, 2019, 07:05	#2
SwissXC90 Premier Member Last Online: Mar 20th, 2024 18:26 Join Date: Jan 2016 Location: Cross Country	It'll be one of the folloiwng: Sticky mechanicals inside the actual door lock Failing microswitch inside the door lock Broken wires in the flexible wiring loom between car body and door To diagnose do this: Take off the door panel and inspect the mechanicals, see if you can find anything sticking and not moving freely. Measure the lock/unlock signals with an oscilloscope and look for noisy signals indicating poor microswitch contact. If so, replace lock mechanism (as switch is buried deep inside the lock) Wiggle the door cable while an assistant locks and unlocks the car, see if you can reproduce the problem to determine if a wire is broken __________________ XC90 R-Design MY2009, Black Sapphire Metallic. HP-Sound, RSE, Nav, Tel, ParkingCam, BLIS, ParkingHeater, RestHeat, Removable Towbar, Summer: CRATUS 20x8 on Pirelli Scorpion Zeros 255/45, Winter: NEPTUNE 17x7 on Continental WinterContact 4x4 235/65.

May 9th, 2019, 08:21	#3
MikeS100 Premier Member Last Online: Mar 21st, 2024 21:39 Join Date: Oct 2011 Location: Sevenoaks	Thanks SwissXC90. I dont have access to an oscilloscope but I can try with an assistant wiggling the wires. If it's not the wires then I guess I will try swapping the lock __________________ 1999 V70 TDi (auto) 2002 C70 T5 GT Convertible (manual) 2008 XC90 D5 Executive (auto)

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