BobbyT

The door locks on my 2000 RX300 operate intermittently. Sometimes when I lock the doors with the remote, I hear a "thunk" as the doors lock, but then a few seconds later, the thunk repeats as the doors unlock (without being commanded).

Sometimes the door locks will operate perfectly for several days, then act up again.

Any ideas on how to troubleshoot and repair this system?

salimshah

Under normal conditions, the door must be fully closed to lock. If a door is partially closed (first catch) then it tries to lock and then unlocks.

The door lock houses all the door ajar sensor, and the door lock sensor. Once you eliminate he half-door-closed part by physically making sure the door is fully closed, it might be time to replace the door lock mechanism. $$$

Salim

BobbyT

Hi Salim,

Thanks for the quick response. This fault occurs when all the doors are fully closed.

I assume each door has its own door lock module. How do I determine which door lock mechanism needs to be replaced?

BobbyT

I have the shop manual, and I'm reviewing the test procedures under "BODY ELECTRICAL - POWER DOOR LOCK CONTROL SYSTEM". If you know a quicker way to isolate which door lock module is defective, it would help greatly.

Or should I focus first on the driver's door lock, since it is used by far the most?

2002RX300

This sounds like the problem I was having. I think it has something to do with the drivers side door lock actuator not working, so all the other locks get a weird electrical signal thereby unlocking after a few seconds.

When you lock all the doors from the remote does the drivers side door actually get locked or does it stay unlocked? If unlocked, then you have a bad door lock actuator. If it does lock then maybe an ECU reset would do the trick.

https://www.clublexus.com/forums/2786328-post15.html

BobbyT

I'm thinking of just going ahead and replacing the driver's door lock actuator. The problem is intermittent, so trying to catch the actuator in fail mode might be more work than it is worth.

Disconnecting the battery or removing the ECU fuse would reset the EFI, but I don't know if it does anything for the central door lock system...

salimshah

Start by locking all other doors and leave the driver-door unlocked. Then try the locking and see what happens. You can move to the next suspect lock and so on. <= This is not a fool proof test, but will point to the bad lock with high probability.

Also make sure your battery is good. People have reported problems with lock when their battery is on the blink. All electronics need good battery.

One more thing, the posts you have seen are about the lock motor. This particular problem has more to do with door close sensor, so lock motor change may not do you much good. ... the lock motor spins multiple turns and there is a limit switch and there may be bad. I would recommend to replace the whole actuator instead of replacing the lock motor.


Salim

BobbyT

Thank you, Salim. Your responses are very helpful. The part I'm thinking of replacing is FRONT DOOR ACTUATOR DRIVER SIDE FRONT (LH) 69040-48020. Does this part also include the door close sensor?

I found this part new on ebay for $199, which appears to be significantly discounted from list price. Do you know of a good source for Lexus parts at reduced prices?

salimshah

Looks like the right part number, but please check with Lexus Parts. I can only vouch for Lexus Parts through the dealer or one of the sponsors here.

Salim

code58

Bobby,
I have worked on several of these and can tell you for a fact that even with 2 or 3 bad actuators the remote will still lock and unlock the actuators that still work. Before you throw away $200.+ on an actuator and the time to replace it, I would do more diagnosis. Does the "door ajar" light on the dash go out when all doors are closed? Do you have more than one remote and do they both respond the same way (IF you have 2)? If you roll the window down and use the inside door lock button (from outside the car) to lock and unlock, does that work properly or does it also do the "lock, unlock" thing? I personally don't think it's the DS actuator, although there's a very, very small chance it could be. Try the things I suggested and report back.

Bobby, where are you in Ca.?

BobbyT

Code58,

I'm in Redlands, near San Bernardino.

I'll hold back on replacing any parts and do some more diagnosis.

The problem appears when I lock the doors using either remote. I hear the locks "thunk", then a few seconds later, the noise repeats as the doors unlock, so I think the system is getting a "door ajar" input from one or more doors. I suspect the driver's door, just because it gets so much more use, but I haven't narrowed it down yet.

Diagnosis is difficult because the locks work correctly most of the time. I'll try your suggestions today and get back to you.

Thanks for your help.

BobbyT

I did some testing, and here is what I observed:

Both remotes seem to operate the same. They send the lock/unlock signals correctly, as shown by the security light blinking and the "thunk" locking sound.

The door ajar light is never lighted, unless a door is actually open, or partially open.

Both rear doors lock and unlock perfectly every time, whether controlled by a remote or the master locking switch on the driver's door.

The driver's side door fails to lock at least half the time, whether remote or master switch is used.

The passenger door fails to lock about 25 per cent of the time, whether remote or master switch is used.

Conclusions so far:

1. Remotes are okay.
2. Rear door actuators are okay.

BobbyT

Unlocking always works perfectly, whether by remote or driver's door master switch.

code58

Bobby,
the one question you didn't answer is the one about whether the doors do the lock-unlock thing when operated from the inside switch. I said to roll the drivers window down and then use the INSIDE switch from the OUTSIDE through the open window, not thinking about the fact that it is a pretty sophisticated system, compared to many others and may be designed to disallow you from locking and unlocking with the window down. Tell us if you can whether it does the L-Unl (uncommanded) from the inside switch.

BobbyT

Yes, it does the lock/unlock (uncommanded) when operated from the inside switch.

Are there any parts in the door lock system that might need to be cleaned or lubricated?