328 Central Locking - How Does It Operate

This is a stupid question - can someone with a UK-spec 328 GTS explain to me how their central locking operates.

According to my Owners Manual I should be able to lock/unlock both doors by inserting the key in either door.

But on my car when locking/unlocking the drivers door with the key the passenger door will also lock/unlock as expected with central locking. However the reverse does not happen if I lock/unlock with the key in the passenger door.

A local 'expert' tells me the manual is wrong - that central locking is only a feature available on the driver's door. So looking for confirmation from someone who actually knows these cars

 

Thanks for the replies. Much appreciated.

 

OK, I have taken both door cards off the car and the door locks are each attached to an actuator switch - grey on the drivers side, and black on the passenger side. I have tested and there is power to both actuator switches - the grey one takes power from the loom, and the black slave takes its power from the grey master in the drivers door.

The black switch actuator has a motor in it which opens/closes the lock when you activate the drivers door.

However, the grey switch actuator has no motor in it - indeed there is no motor in the drivers door.

Therefore I can't fathom out how opening/closing the passenger door with a key can also open/close the drivers door, as there is no motor in the drivers door.

Now totally lost!

 

Is there anyone here in the UK who has a 328 and lives in the Bristol area - so I can compare my car's operation to yours?