How can i fix central locking in 1999 audi a4?

You will need a key that does work before you can reprogramme your central locking. If you do, try this.

Electronic key codes are assigned to each key by the manufacturer. The central locking pump can store the codes of up to four keys.
If one key must be programmed, always program ALL infrared keys.
This complete procedure must be repeated to program each infrared key.

- Move the vehicle to an area not illuminated by fluorescent lights.
Programming sequence will not work properly under fluorescent lights.

- Switch ignition ON using a second key.

The next three steps must be completed within 30 seconds. Otherwise, procedure will have to be repeated.

- Close and lock all doors with the mechanical door locks. (LEAVE A WINDOW OPEN IN CASE IT DOESN'T WORK)

- Point infrared key to be programmed at either infrared sensor and briefly press the transmitter button from one to four times.

Note:
Pressing the button once will program the key as Key No. 1; pressing it twice will program the key as Key No. 2, and so on.

The sequence of the transmitter pulses must occur in one second intervals, and the sequence of up to four pulses must be completed within five seconds.

The anti-theft alarm will sound the horn briefly after each signal to confirm reception.

- Press button ten seconds after entering the last pulse. Vehicle will unlock and programming for that infrared key will be completed.

If the doors still don't lock/unlock then you may find that the infrared system has shut down at some point. It can be reactivated as follows:

- Press infrared key transmitter button while pointing key at infrared sensor.

- Within one minute of pressing transmitter button, manually unlock either door.

- Infrared system is now reactivated.

Hope this Helps mate.

Paul
April 2005