Central locking does not lock rear doors.. but tries to [RX400h]

mikobg · February 21, 2021

Hello all!

As per the odd topic title, I have recently purchased an RX400h, which I'm very happy with. Since it's an old car now ('07) it obviously needs some TLC, but i'm also happy to do that.. so I started with a few things, one of which is the rear doors were not locking when locking the car.

The doors would not lock with the key or through the driver's door button, but in both cases the car does try to lock them and you can see the locking buttons inside moving rapidly, but then ending up unlocked. So, i thought the issue here would be either the cables or the actuator itself.. so I bought 2x actuators to replace on both rear doors.

I did this today and upon initial testing (before fully assembling the door panel) things seemed fine - the car locked the rear door with the new actuator and then unlocked etc. Then I plugged in the window control button and it went straight back to the old behaviour where it just wouldn't lock. So.. i thought it might be connected to the other side's door not working properly and I went ahead and changed that actuator too. It initially started working... but then once I assembled everything back together it would lock the doors occasionally.. then it wouldn't and so on. It's quite random unfortunately. Then I got to a point where it would 100% lock all doors, but would not always unlock on of the rear doors and I thought fine - this is better than leaving it unlocked and thought I would call it a day until I find more information. Well all was well until I parked the car back in my garage space, which is quite steep. I left the car, used the key fob to lock and it just would not lock the rear doors again.

I tried searching the forums for similar issues, but did not find anything, so I apologise if this has been discussed already.

Any help on this would be highly appreciated!

-Alex

m4rkw · February 21, 2021

If you've already replaced the actuators it sounds like its tripping a safety mechanism of some kind, if you turn the key to position 2 with all doors shut is there anything on the dash that indicates one of them is still open?

Failing that I would recommend taking it to Electrum in Wimbledon if they're not too far away. They're very good at stuff like that.

mikobg · February 21, 2021

2 minutes ago, m4rkw said:

If you've already replaced the actuators it sounds like its tripping a safety mechanism of some kind, if you turn the key to position 2 with all doors shut is there anything on the dash that indicates one of them is still open?

Failing that I would recommend taking it to Electrum in Wimbledon if they're not too far away. They're very good at stuff like that.

Hi m4rkw, thanks for the prompt reply!

There's nothing on the dash indicating an open door when they are all closed. I thought so too, and tried each door and it would indicate that it's open only when it's actually open, so door sensors seem to be fine.

I'm currently not in the UK at all, so it's not an option unfortunately, but if I can't seem to sort this out I will seek out a garage for help at some point.

m4rkw · February 21, 2021

Oh also if you have techstream it'd be worth checking for codes, maybe you have fault with one of the security modules.

m4rkw · February 21, 2021

The fact that it's both rear doors but the fronts are ok seems like a clue. If there are no codes logged maybe see if you can track down a wiring diagram and see what electrical components are common to the rear doors but not the fronts.

mikobg · February 21, 2021

I should also add that the manual "button" on the inside of the doors that should lock/unlock the doors manually from the inside is very stiff and hard to operate.. but doesn't seem to operate properly as well even after the actuator change, which comes with cables.

m4rkw · February 21, 2021

5 minutes ago, mikobg said:

I should also add that the manual "button" on the inside of the doors that should lock/unlock the doors manually from the inside is very stiff and hard to operate.. but doesn't seem to operate properly as well even after the actuator change, which comes with cables.

Ohhh. It's a cable issue. You've connected the bowden cables wrongly somehow, or they aren't quite seated correctly. I think I did this on mine once after taking one of the door cards off, the inner mechanical switch became rock hard. I seem to remember on mine the end that goes to the outer handle was somehow not quite seated correctly, so it was very tight when attached to the inner handle. I think I just fiddled around with it for a while and got lucky at some point, I never figured out how to actually get to the end of it that's attached to the outer handle.

I'm betting you have something similar as that would explain the symptoms - it's trying to lock but it can't because the cable isn't attached properly and can't move as it should.

mikobg · February 21, 2021

Okay, i might try to attach it properly even though I read that people glue these on to the brackets, but mine never came off the bracket. I might try having some electrical tape around the plastic bit that goes in to the bracket to make it stick there firmer and see if this changes anything. I also just purchased a techstream diagnostic so waiting on that in a day or two to see if anything pops on it. I will keep this thread updated for sure! 🙂

m4rkw · February 21, 2021

The mechanical inner switch on the doors uses the bowden cable to lock and unlock, so if that is really stuff that's a strong indicator something is wrong with the way the cable is attached, or it's caught on something further up.

Illogan · February 21, 2021

1 hour ago, m4rkw said:

The mechanical inner switch on the doors uses the bowden cable to lock and unlock, so if that is really stuff that's a strong indicator something is wrong with the way the cable is attached, or it's caught on something further up.

Or possibly a fraying cable is catching inside the outer sheath - - are they routed round a 90degree (or more) bend maybe?

mikobg · February 23, 2021

Okay so I got techstream today, which didn't return anything related to the doors/locks. Meaning the issue is most likely mechanical.

I will go ahead and tighten the brackets that hold the cable in place on the inner side of the handle, hopefully prevent them from moving if that's the issue. If this doesn't help, I'll be even more at a loss since I have no other ideas currently.

@Illogan There's no bends on the cables that I know of. They go in a pretty straight line from the actuator to the inner handle, so i don't see how they could be bending.

m4rkw · February 23, 2021

26 minutes ago, mikobg said:

Okay so I got techstream today, which didn't return anything related to the doors/locks. Meaning the issue is most likely mechanical.

I will go ahead and tighten the brackets that hold the cable in place on the inner side of the handle, hopefully prevent them from moving if that's the issue. If this doesn't help, I'll be even more at a loss since I have no other ideas currently.

@Illogan There's no bends on the cables that I know of. They go in a pretty straight line from the actuator to the inner handle, so i don't see how they could be bending.

I'm pretty sure I had your exact symptom once on one of my rear doors after messing about with a door card. I think the cable was caught on something on the outer side of the door.

I just dug through my emails as I remember emailing a mechanic friend when it happened, this was back in August 2018:

"I just popped a rear door card off to check the size of the speakers and had a strange issue when I put it back on. There are two bowden cables in the door, one for the handles which is all fine and another for the interior lock switch.

When I put the door card back on I noticed the lock switch was stuck in the locked position. I took the card off again to have a look and it seems that the bowden cable is in the right place but there is so much tension on it that the switch can't move. I'm pretty sure it's on right as there's no other way it can go on and still be held in place.

Strangely, despite the switch being stuck in the locked position, if I use the central locking with it in that stuck position the door stays unlocked.

For now I disconnected the bowden cable internally, which allows the central locking to work. But I'm really baffled as to what's happened here, the only thing I can think of is that something must have slipped at the other end of the bowden cable."

After a conversation and a follow-up I mentioned that yanking the cable got it loose from whatever it was stuck on. Obviously be careful if you decide to try that.

mikobg · February 27, 2021

Hey all!

I managed to sort the issue with my rear doors, so I'm sharing here in hopes this might help someone else in the future!

What was wrong is the cable had slipped out of it's ending tip (blue on the photo below) and when the car tried to lock it, the cable would just bounce back out and unlock the door. What I did was stick the cable back in it's tip firmly, then used ducktape to tape it in place. I used a lot of tape to make sure it doesn't move and it's very firmly taped too. (Tape the blue tip to the black cable covering so it doesn't slip out again) One of the doors had this issue at the actuator's end, the other had the same issue, but with the handle's end.

Here's a photo for better explanation:

m4rkw · February 27, 2021

Nice one! I knew it had to be a cable issue. Glad you got it sorted. I didn't ever manage to figure out how to get to the outer handle attachment end with mine, I just got lucky by yanking it a bit 😄 When i mentioned this to my mechanic friend he said "I would rather be lucky than highly skilled".

Illogan · February 27, 2021

Thanks for that information and pics Alex

mikobg · February 27, 2021

4 minutes ago, m4rkw said:

Nice one! I knew it had to be a cable issue. Glad you got it sorted. I didn't ever manage to figure out how to get to the outer handle attachment end with mine, I just got lucky by yanking it a bit 😄 When i mentioned this to my mechanic friend he said "I would rather be lucky that highly skilled".

Wise words from your mechanic friend indeed! 😄

Otherwise, I didn't need to get to the outer handle end, but it shouldn't be too hard ~~after removing the plastic cover. 🙂~~

*EDIT: I actually remember on my old BMW X5, outer handles were disassembled from the outside too, so it's probably the same with Lexus.. if you ever need to. 🙂

Edited February 27, 2021 by mikobg
Added more info