A3 remote locking and unlocking

[Violetob]

Hi, having now replaced the regulator on my daughter in laws A4 I now have to move onto my grandsons A3. 

 It is an Audi A3 2005.

The unlock on the remote does not unlock the the doors, but when you use the remote to lock the doors it all works OK.

I have replaced the cell button battery in the key fob just to be on the safe side. Was wondering if there is a module somewhere that may need replacing,

if so where would it be found.

any help appreciated, thanks in advance.