Ls400 Ucf11 1993 Car Alarm Problem Central Locking

bazgtr · January 15, 2011

Before I start stripping down the system has anyone had this before.

My mum borrowed the car in the week and since then the car alarm just keeps looking the doors at all times.

To get in you have to press the button and pull the drivers handle within half a second or the door will relock.

Car starts and drives all ok and once you park and get out the door will lock on the button, But sometimes the car doesn't reconize the key fob and you have to do it by the key. If I leave the car for a few seconds the car will auto lock. If I come back to the car after a hour or in the morning the car will open by key fob correctly but then start to play up again.

Any ideas?

I think it would be an earth somewhere but anyone got any ideas which earthing point it might be or is there anything else I need to look at before I open the can containing the worms.

Baz.

SteveLS400 · January 15, 2011

Before I start stripping down the system has anyone had this before.

My mum borrowed the car in the week and since then the car alarm just keeps looking the doors at all times.

To get in you have to press the button and pull the drivers handle within half a second or the door will relock.

Car starts and drives all ok and once you park and get out the door will lock on the button, But sometimes the car doesn't reconize the key fob and you have to do it by the key. If I leave the car for a few seconds the car will auto lock. If I come back to the car after a hour or in the morning the car will open by key fob correctly but then start to play up again.

Any ideas?

I think it would be an earth somewhere but anyone got any ideas which earthing point it might be or is there anything else I need to look at before I open the can containing the worms.

Baz.

Do you happen to know which security system is fitted to your car? As far as I know, they were not factory fitted - certainly not in the MKIII anyway. Also, do you have any instructions for the system? I'm assuming not. They would probably tell you how to re-set the fob to the car. I have searched this forum and found nothing useful.

Rather than start stripping the car, have a look at the fob 1st. Is the Battery in it still good? Did mum accidently change a setting on it? Did she inadvertantly press it that hard the button is somehow stuck? It could be purely coincidence that it started to play up after mum borrowed the car.

Are all the doors, boot etc all shut correctly and nothing fouling the sensors?

steve2006 · January 15, 2011

There have been problems with the courtesy light door switches causing random faults,easy to remove, check and clean them before going in deeper.

bazgtr · January 15, 2011

Just a quick update on this.

The alarm is a factory one and the Battery and fob etc are OK.

Have reset the factory alarm as stated by Lexus and all now seems fine tonight anyway. I did find that the rear drivers side door closed sensor was a little sticky so now free and loose and all OK after resetting the alarm as stated before.

Just hope in the morning it still works OK as seemed worse in morning with the dam etc. If not then I'll change the theft deterrent system ecu and go from there.

bazgtr · January 22, 2011

Problem still there when it starts to play up it locks the doors straight away after opening the central locking with the remote. Secuirty light does go out and on as it should but keeps locking the doors.

Switches in doors seem OK and as it lights up in the dash as it should when pressed.

Have now changed the theft deterent ECU and problem still there.

Weather is not a factor as doing it in rain or dry weather.

A/E next port of call.

Will list problem once found later in the next week.

PS STEVE

Have you heard of the key warning switch sensor on the ignition barrel playing up? I ask this, As when you turn the key once and press in and out a little the central locking tries to lock the doors. Wondering if its cracked or something as my mum is very heavy handed and ramed the key in the ignition barrel when she took the car.

Manc · January 24, 2011

Are you sure one of the locks you push by hand is not sticking.... my passenger door will not lock automatically... it just goes half way and then releases again... i have to walk around and manually lock it with the key.

And before you strip the alarm - strip the door panels & try lubing the mechanisms with silicone grease - the front doors should be the culprit...

Good luck

bazgtr · February 2, 2011

Well after arranging the auto tech to come after the car would not respond to the remote and then will only open the car compared to just shutting the car a few weeks ago. The problem has now gone.

Got home and used the key to lock the drivers doors and everything on the car worked as it should with a bit more noise than normally as like it has reset itself. The doors locked and then alarm light came on. With that in mind I think my mum must have forced the key in the barrel a little hard and somehow upset the sensor on the back of the door lock barrel as mentioned in previous thread by other member.

Two weeks on and the car is all good.

In the end of this the lesson learnt is that go and by my mum a new car as I did, So she can't borrow mine.