Avensis 2001 - Strange Central Locking Problem

[eleutheros]

I've been searching these forums for a while now trying to find help for my particular problem, but after trying some of the recommended solutions I've figured I've got to open up a topic of my own. Hopefully some of you will take time to help me.

My car is a 2001 Toyota Avensis, 1.6.

I will sort the problems into those which are permanent and those that only happen from time to time.

Firstly, the central locking system will not unlock the car from the key fob, either wirelessly or when the key is turned in the door. However, it locks every door just fine, and the button on the door can be used to both open and shut all of the locks.

When I click the "unlock" button on my key fob the lights flash twice, but nothing happens.

Furthermore, from time to time when I get back to my car, it has unlocked itself! This happens quite frequently now, and really worries me. It also "clicks" when driving, and if I use the button the drivers door to lock it, it will usually quickly unlock itself.

Now, these are the things I've tried: removing the car Battery for more than ten minutes, removing what I think is the wireless ECU (a black box situated under the steering wheel) several times (I even left it disconnected, and returned to find that the central locking had unlocked itself overnight). I have also tried various methods for resynchronizing the key with the locking system, but none of these seem to work (I get no response from the system).

I'm especially confused by the fact that the car unlocked itself when the wireless ecu was disconnected. Does this mean that the problem is somewhere else? Where should I look next?

I've taken it to the garage once, and they thought the problem was with the wireless ecu, but they weren't sure. I thought it was too expensive to replace (they wanted around NOK 5000, approx. £500 for it), but now I'm not convinced that would even help.