Hi recently my 99.5 a4 b5 wont lock by using the key, but it will unlock the car using the key. I know its not a vacuum pump problem because it locks and unlocks just fine when pressing the button from inside.

Does anyone have any idea on what could be wrong with the locking using the key?

 

Hmm, strange. Does it feel loose trying to lock it compared to unlocking it? Maybe take off the door panel and see if something looks out of place.

 

When you say it won't lock using the key, do you mean you can't put your key in the lock and turn it to the unlock direction? Or do you mean it won't unlock with the remote button on the key?

 

He means the key in the cylinder wont lock the car but it will unlock the car. The remote works fine to lock and unlock the doors.

Sounds like its just a frozen cylinder or its broken and needs replacing. Theres really no other variable.