Passenger door does not open from the outside after using any unlocking procedures. Will finally open if you use inside passenger door handle and will always open until you re-lock doors. The whole cycle will start all over again after re-locking doors.

SOURCE: the door lock won't unlock from the inside

check out the motor in the door

SOURCE: audi a4 1995 central locking problem

Hi there.
I had exactly the same problem and there are 2 ways of solving it. The first is to pay your Audi Service Centre £350-£550 to replace it for you and the second way is to do it yourself which will cost well under £100 (depending on ebay). Firstly check the Central Locking Pump to make sure the hoses haven't come off. This is located in the very back right hand corner of the boot so you will need to remove the carpet and internal trim and you will see a block of sponge. Carefully lift the top off this and you will see the pump sat inside it.
Actually there is a great set of photos online to help you and I will add the link for you at the end. If the hoses are still connected and not leaking it is very likely that the internal compressor wheel has shattered (quite a common fault). I believe it is possible to open the pump and replace this wheel (in fact there is one for sale on a very popular auction site at the moment) but my own preference was to simply buy a whole new pump and replace that (£16.00 + £8 p+p off the same auction site).
The most important thing for you to remember is that when you look to buy a replacement pump you need to find one with the EXACT same serial number. The one in the diagram shown is
8LO 862 257 N but I have a sneaky feeling yours might end in an A.
Anyway, I hope this is of some help and dont worry about the connections as both air connectors and all 3 electrical ones are different sizes and will only fit in one place each.
Good luck.
Rik

http://www.audiworld.com/tech/elec131.shtml

SOURCE: 2001 Ford Explorer Sport Trec - rear passenger door handles

only way to repair is to replace the handles. this is a common problem they use a toothed circle to work the lever and it wears and jumps a tooth basically and it will pop the tooth off if you push it back.so replacement is only fix

SOURCE: 2001 A4 Quattro Back Seat Passenger Side Door

There is a child lock on it. Open the door and look on the edge of the door, where it mates to the body when the door closes. There's a lever there that is labeled as the child lock. It'll show her which way to switch the lever to allow the door to be opened from inside the car.

SOURCE: Front passenger door won't open from inside - 2004 Dodge Intrepid

Door panel will have to come off to repair, most likely has broken door handle or cable/linkage problem.