RX300 (2002) random alarm question

[ScotGold]

Sorry to bother you with another RX300 alarm issue. I have checked previous threads and tried some of the suggested fixes but without success.

A few weeks ago the alarm started sounding at random when the car was in a locked status. It usually happened up to 10-40 minutes after I had locked the car. Everything else seems to be working. I installed new batteries in the two remotes and grey sub key = no difference. I have a temporary fix by retaining one black key in the ignition and manually locking the driver's door with the other. Hardy satisfactory but it works.

Any tips or suggestions would be welcome. Thanks - Chris

[PaulDD]

I have the same problem mine is an early 2002 version RX300. Have you tried closing all the doors then inserting the key in the drivers door turning the key it in the "unlock" direction (even though the car is already unlocked) remove the key and within 10 seconds press the lock button on the key once to lock the doors or twice to deadlock the doors.  
This leaves the alarm/immobiliser activated but interior sensors off. This seems to have cured my problem or more accurately isolated where the problem is IE. in the interior sensors system.  The PITA is that you have to use this system every time you alarm the car. 
 

Does anyone know if (on my early 2002 RX300)

1. is there a way to perminatly disable the interior sensors?
2. is it an ultra sonic or proximity sensor system?
3. where the sensors are located?
4. How do i permanently cure the issue?

I have read many of the threads but the problem is its often unclear whether these "cures" are like the one above and needs performing every time I lock the car or not?