Hi,i have something similar wrong with my Octavia 1.9tdi[2007],same thing as you,i unlock my car and get in,and before i can get the keys into the ignition it locks up,but if i put my keys into the ignition it unlocks immediately,interior light dont come on when the drivers door is open and when i leave the lights on by accident the ringing tone dont come on,but these always worked up to 6 months ago and now nothing..  

I have the same problem with my Octavia 2004 tdi,also when low on diesel light comes on there is no warning sound,roadhog1 did you manage to find out anything ?

Hi,i have something similar wrong with my Octavia 1.9tdi[2007],same thing as you,i unlock my car and get in,and before i can get the keys into the ignition it locks up,but if i put my keys into the ignition it unlocks immediately,interior light dont come on when the drivers door is open and when i leave the lights on by accident the ringing tone dont come on,but these always worked up to 6 months ago and now nothing..  

 

Yeah, it's definitely a failed microswitch on the driver's door lock unit. Very common fault, they are absolute rubbish. Mine does exactly the same thing. I can get around it by either turning on the ignition before 30 seconds or opening the rear passenger door, because the switch in that door still works as it gets nowhere near as much use. Typical symptoms are no lights-on warning alarm and interior light not coming on when driver's door opened. At the moment I can't be bothered to strip the driver's door down so I'm just living with it, but it's a pain in the arse.

Door module

 

My Golf did this.

 

Especially if not buzzing when door opened and lights on (my golf!)

 

Basically it doesn't see that you have opened the door, so after 30 secs or w/e its designed to relock - as it thinks the door hasn't been opened so must have been a mistake (walking away from the car or w/e in your pocket)

 

So diagnosis is a new door switch. My new fabia on the other hand buzzes when I open the door with the lights on, and once I open the door after unlocking - it no longer locks itself (which is much better than my scary golf deciding to go AWOL and lock itself!)

With this sort of fault in the lock/unlocking system would this cause an MOT failure?