My car is a 2001 A4 1.8T,
A problem suddenly happened the other day. all door locks seems not working any more... I press the lock button on master key, the red LEDs by the front door windows flash, a horn will confirm all door are locked, but actually none of them can lock. and a strange little motor sound came from the trunk by the fuel tank cap. confused... Please help.

 

please help.

 

You probably have a faulty pump. Oh, the vaccum lines that power the actuators that actually lock the doors, may be pinctured or cracked and are gonna need replacement.

This problem just started for me..as soon as a few weeks ago. I did some research and now I know what the problem is. A quick VAG-COM scan will confirm that it's the pump or vacume lines for the locking system that are at fault.
I'll have it fixed soon and i'll let you know how it goes.

 

if you manually lock with the key does it work ?

is it consistent or just happens sometimes ? my friend's mark v rabbit had a similar issue, had the locks replaced under warranty

 

Could be that your trunk latch is broken and affecting the rest of the locking system. I've heard it happen before to a few people, just have the trunk latch/locking mechanism replaced depending on what is faulty and you should be good to go again hopefully.

 

Hi, have you been able to solve your problem? I have the same issue and I am looking for a repair manual but have not been able to find one on the web that could allow me to locate the door lock vacuum pump to diagnose if there is a faulty connection.

Thanks for your help.

 

Yeah, I found and fixed the problem. It was a broken plastic piece that attaches the vacuum line to the door lock om the front passenger side of my car. I dismantled the whole door and guts and fixed it. I took pictures of the whole fix, I can send them to you if you want. It was actually pretty simple.
Your problem may be different, try to listen around the car to find any unusual sounds.

 

can you post the pics. I have a 1999 a4 quattro. I just messed with the dash, but didn't do any thing to the doors, but now they will not lock or unlock from the remote, or the switch on the doors.

 

Can you send me the pics to my email venkata_gr@yahoo.com.

I have similar problem. ( Audi A4 Quatra 2001 model )

 

i had the samr problem but had to replace the pump as it is known to shatter inside. replaced it and havent had a problem