Reset anti theft system on a 99 audi a4

One of the simplest ways to do this is to lock all the doors manually if you can, stand outside the car with your key in hand. Insert the key into the driver door key slot and turn it to Lock, Lock, Unlock, Unlock. That should tell the vehicle that it is supposed to turn off the anti theft. This can happen whenever the battery dies or looses power for whatever reason. It also happens frequently when someone locks their keys in their car and a towman or locksmith opens their door for them. Those professionals should have done the reset as part of their process though.

Very fine German engineering, you can't. The anti theft system is there to stop exactly what you are trying to do. You can't get around the anti-theft module and it connection to the ECM (a mini computer and a big computer protecting your vehicle from thieving ne'er do wells!). You have to fix what is wrong, not find a way around it.

Mobile auto electrician, alarm installer or dealership to diagnose with a $5,000 pro grade scan tool computer and fix.

Or perhaps, it just needs resetting? Did you disconnect the battery. We need the whole story.

https://www.google.com/search?q=audi+a4+anti+theft+reset

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IMPORTANT NOTE:
You must have the security anti-theft code for your Audi radio from the car manufacturer, or from an Audi dealer!

You can find the radio code at: http://www.radio-code.co.uk/

The sequence of programming for 1997 Audi A4 radio is:
1. Push simultaneous "SCAN" and "RDS" keys until on the screen will appear "1000" displayed.
2. Release keys. No more push on "SCAN" and "RDS" keys because otherwise number "1000" will be considered as first safe code attempt.
For example: we have the security code "5079". Then:
3. By the no.# 1 key you will set up the first safe code digit. Push 5 times on the no.# 1 button. The "5" number will be setted.
4. By the no.# 2 key you will set up the second safe code digit. Push 10 times on the no.# 2 button. The "0" number will be setted.
5. By the no.# 3 key you will set up the third safe code digit. Push 7 times on the no.# 3 button. The "7" number will be setted.
6. By the no.# 4 key you will set up the four-th safe code digit. Push 9 times on the no.# 4 button. The "9" number will be setted.
7. Then push again simultaneous "SCAN" and "RDS" keys for confirm this safe code. On the screen will be displayed "SAFE" notice. Release keys! For few seconds a radio frequence will be displayed.
The radio is now ready for use!

Wait one hour before attempt to put again the correct code!!! Now the radio is under anti-theft protection. IMPORTANT NOTE: You must have the security anti-theft code for your Audi radio from the car manufacturer, or from an Audi dealer!

The sequence of programming for 1997 Audi A4 radio is:
1. Push simultaneous "SCAN" and "RDS" keys until on the screen will appear "1000" displayed.
2. Release keys. No more push on "SCAN" and "RDS" keys because otherwise number "1000" will be considered as first safe code attempt.
3. By the #1 key you will set up the first safe code digit.
4. By the #2 key you will set up the second safe code digit.
5. By the #3 key you will set up the third safe code digit.
6. By the #4 key you will set up the four-th safe code digit.
7. Then push again simultaneous "SCAN" and "RDS" keys for confirm this safe code. On the screen will be displayed "SAFE" notice. Release keys! For few seconds a radio frequence will be displayed. The radio is now ready for use!
Please do rate my response. Thanks!

IMPORTANT NOTE: You must have the security anti-theft code for your Audi Concert radio from the car manufacturer, or from an Audi dealer!

The sequence of programming for 1998 Audi A4 Concert radio is:
1. Push simultaneous "SCAN" and "RDS" keys until on the screen will appear "1000" displayed.
2. Release keys. No more push on "SCAN" and "RDS" keys because otherwise number "1000" will be considered as first safe code attempt.
3. By the #1 key you will set up the first safe code digit.
4. By the #2 key you will set up the second safe code digit.
5. By the #3 key you will set up the third safe code digit.
6. By the #4 key you will set up the four-th safe code digit.
7. Then push again simultaneous "SCAN" and "RDS" keys for confirm this safe code. On the screen will be displayed "SAFE" notice. Release keys! For few seconds a radio frequence will be displayed. The radio is now ready for use!
Please do rate my response. Thanks!

IMPORTANT NOTE: You must have the security anti-theft code for yours Audi radio from the car manufacturer! The sequence of programming is:
1. Push simultaneous "SCAN" and "RDS" keys until on the screen will appear "1000" displayed.
2. Release keys. No more push on "SCAN" and "RDS" keys because otherwise number "1000" will be considered as first safe code attempt.
3. By the #1 key you will set up the first safe code digit.
4. By the #2 key you will set up the second safe code digit.
5. By the #3 key you will set up the third safe code digit.
6. By the #4 key you will set up the four-th safe code digit.
7. Then push again simultaneous "SCAN" and "RDS" keys for confirm this safe code. On the screen will be displayed "SAFE" notice. Release keys! For few seconds a radio frequence will be displayed. The radio is now ready for use!

This is from Ken on CarPros:
Here is the way to reset the security system.

https://www.2carpros.com/articles/how-to-reset-a-security-system

Here is the systems descriptions

There are 2 security system, namely anti-theft and immobilizer.

Here are the 2 systems.

DESCRIPTION & OPERATION
Anti-theft system is controlled by Body Control Module (BCM). BCM receives signals from hood switch, trunk switch, door switches and Local Control Modules (LCMs). There are 5 LCMs located throughout vehicle.

To set anti-theft system in armed mode, remove ignition key, close all doors, trunk and hood. Lock doors using key or remote controller. The SECURITY light will illuminate for 30 seconds, then flash in 2.4 second intervals, indicating system is in armed mode.

To cancel armed mode, unlock and open any door or trunk lid using key or remote controller. SECURITY light will flash every second, indicating system is disarmed.

Alarm will activate (horn sounds, headlights flash and starter circuit is disabled) if any of the following conditions occur while system is in armed mode:

Engine hood or trunk lid is opened using the hood or trunk lid release.
Door(s) is unlocked without key or remote controller.
Tampering with any door/trunk lid key cylinders.
To deactivate anti-theft system, unlock door or trunk using key or remote controller.

If it is the immobilizer that is preventing the engine from being started, ensure you have the correct key and the transponder is intact. Quite often keys are dropped and if it breaks open, the internals would scatter all over. When this occurs, there is a tendency for the transponder to be lost.

Please let us know happens so it will help others.

Best, Ken
I hope that helps you out!

Check the underhood relays. Wiggle each one and see what happens. Check all the fuses that pertain to these operations also.

With the doors shut, insert the key into the drivers door lock. Lock and unlock the door 5 times. This should reset the system. If that doesn't work you should contact a qualified repair shop.