ok first if you can go to Autozone to rent the Code reader scan tool. This is free to us but you need to give a deposit first and then you get it all back when you return it. Take it home and plug it in to the computer connection and then just follow the instruction to read the codes that are stored in the computer. Now it is common for it to have the code 17978, or P1570 If it does have these codes here is what is going on and what to do about it.
The vehicle starts and stalls. Trouble code P1570 (17978). The security light is flashing.
Tests/Procedures: 1. As of model year 2000, Volkswagen has changed the immobilizer system and the 7 digit PIN numbers are no longer available to the aftermarket. These vehicles all now use the Volkswagen GeKo (GeKo is a German acronym from the term Geheimnis und Komponentenschutz. In English this means Security and Component Protection. GeKo is the name Volkswagen used for the Security and Component Protection process.). Retrieval of immobilizer codes can still be performed with any Volkswagen compatible scan tool, but adapting new keys or any procedure requiring the 7 digit PIN number (Replacing Engine Control Module (ECM) or Instrument Panel (IP)) requires the vehicle to be serviced by a Volkswagen dealer using the GeKo system. 2. Acquire any extra keys from the vehicle owner and try to start with different keys. Should the vehicle start with an alternative key this would indicate a bad key. A new key should be purchased and programmed at a VW authorized repair shop. 3. There have been good results by performing a vehicle cold re-boot for restoring immobilizer functionality without the need for programming due to logic locked modules. Disconnect both battery cables and momentarily touch them together. Leave disconnected for 15 minutes then reconnect. Attempt to start the vehicle. 4. An alternative method is leaving the vehicle key in the ignition with the key on and engine off for 1 hour (note: it is a good idea to place a battery charger on the battery during this procedure to prevent battery voltage going low. In addition, apply the emergency brake to disable daytime running light function). This procedure can cause a key relearn to occur and reestablish normal anti-theft operation and vehicle starting. 5. If the vehicle still does not start, then arrange to have it towed to an authorized dealer.
Active ImmobilizerIgnition KeyLogic LockTech Tips: When the immobilizer is active the vehicle will start and stall after about 2 to 3 seconds and the immobilizer light on the Instrument Panel will be flashing. Diagnostic Codes: DTC 17978, P1570
Now if it does not have these codes you can ask autozone what the codes are and mean if you have it differant. It also could be the BCM Body Control Mogule the computer.