VW Scirocco Immobilizer Fault Kills Engine at Start

I had a similar immobilizer fault on my 2012 Golf GTI. With some experience working on VW electronics, I can share what worked in my case. The symptoms were identical, car would either not start or die immediately after starting. After checking various components, it turned out the key signal was getting interrupted due to incorrect programming. The immobilizer bypass was not an option I wanted to consider, as it could affect resale value. My workshop ran a diagnostic scan that revealed the car immobilizer was functioning normally, but the key programming sequence was corrupt. They reprogrammed the key to properly communicate with the immobilizer module, which solved the issue completely. Total cost was 45€ for the programming service. To better assist with your specific case, could you share: Whether you recently had any work done on the electrical system, If you can start the car with your spare key, What error codes are showing up in the scan, If the issue started suddenly or developed gradually These details would help determine if you are dealing with the same root cause or if your car electronics might have a different underlying problem.

Thanks for sharing your experience. My latest service was done at 16002km and the issue started shortly after. I tried both the main and spare key with no success. The anti-theft system warning light stays on after each failed start attempt. The scan shows error code P1634 which from what I understand relates to the immobilizer circuit. No recent electrical work was done, but the battery was replaced about 2 months ago. The problem came on quite suddenly, worked fine one evening, complete failure the next morning. After reading your response about key programming, I wonder if the battery replacement somehow affected the car electronics or key signal synchronization. The remote start function on both keys still works for locking/unlocking, just not for keeping the engine running.

Thanks for those extra details, your symptoms match almost exactly what I experienced after my battery change. The P1634 code is the same one I encountered on my GTI, which points strongly to an immobilizer synchronization issue rather than a hardware failure. The key programming often needs to be resynced with the ignition control module after power interruptions like battery replacements. While the remote functions still work, the anti-theft system requires a separate authentication process during the start sequence. In my case, and likely yours too, the immobilizer fault was triggering because the key signal wasnt being properly validated by the car electronics. This explains why both keys are affected, its not the keys themselves but their programming thats out of sync. The fix should be straightforward and significantly cheaper than replacing components. A proper diagnostic tool can resync the key programming to the immobilizer module. Most shops charge between 40-60€ for this service. Just verify the shop uses VW-compatible programming equipment, generic scanners often cant properly interface with the anti-theft system on these models. This should resolve the start/stall issue without needing any parts replaced.

Based on that information and your experience, I think I'll schedule a key programming service this week. The security light behavior and matching error code really point to this being a sync issue like you had. Its reassuring to know replacing the immobilizer module probably isnt necessary. Just to confirm, the programming service should work with my existing keys? I dont want to end up needing new keys cut if the resync fails. Also good to know about needing VW-specific diagnostic equipment. I found a shop that specializes in German car electronics so hopefully they can handle the programming properly. The timing with the battery replacement makes sense now. Wish the shop had mentioned this could happen, would have saved me some stress thinking the whole anti-theft system was damaged. At least the fix sounds relatively straightforward and affordable compared to replacing parts. Really appreciate you taking the time to explain your similar experience. Ill update once I get it sorted out.