Yet another C3 central locking issue

[freddyokel]

Hi all,
my o/h has bought a 2012 C3 Picasso 1.6HDi (90hp) VTR+ and... there is a central locking issue.
All doors except the rear left lock (and make a noise) when the fob is pushed but that door is still openable from the outside and inside.
If the 'deadlock' is engaged then the door does make a noise but is still openable from the outside only. The inside catch doesn't open the door in deadlock.
Other oddness includes the car locking all the doors when the you get in the drivers seat and close the door and even when you get out and close the door but this may just be me not being used to whatever 'autolock' is!

We've tried another door lock mechanism which exhibits exactly the same behaviour.
I'm guessing that this a wiring issue either on pin 4 or pin 6 to the module. I don't know which is the deadlock.
Pins 1,2,3 appear fine (the door sensors work) and as the deadlock actuates it can't be pin 5 (the shared motor common).

Any help would be appreciated but obviously I'm hoping that Marc picks up on this.

[freddyokel]

Bit of an update...
Haven't got the door card off at the moment (waiting for new clips) but I've had a look at the 16pin (8 populated) connector in the door jamb and found two pins that pulse 12v when the lock button is pressed.
I'm pretty sure these are pin 4 and 5 on the module (which get flipped either way for locking and unlocking but will both read 12v due to the voltage passing through the other 3 door motors as they are all in parallel)
However, if I meter these out on the door side (with it disconnected) there is infinite resistance where I should see the resistance of the motor coil.
So... Body harness is producing the voltages, the motor coil on my spare module (which also didn't work) is good...
Diagnosis? Door harness is iffy.

[GiveMeABreak]

If the 'deadlock' is engaged then the door does make a noise but is still openable from the outside only. The inside catch doesn't open the door in deadlock.

This is normal behaviour and what deadlocking is supposed to do. When activated with double fob lock press, deadlocking disengages the internal door opening controls so the doors cannot be opened from the inside.

[freddyokel]

It's getting totally weird now.
I've had the door loom out and verified that all eight wires connect to what they should.
Switching the manual child lock switch on the door edge has allowed me to prevent the door being opened from the outside.
The whole system is behaving oddly and changing the child lock switches on the front doors appears to subtly alter the way it works. Which is bonkers.
Time to do a BSI reset and then document every possible configuration I think...

[freddyokel]

I have a suspicion that this may be something to do with the 2nd issue. The weird autolocking...