VW Polo Immobilizer Fault Causing No-Start Issues

I had a very similar issue with my VW Golf 2007 diesel last summer. Had some experience with basic car maintenance but this immobilizer problem was new to me. The security light would flash and the engine would crank but not start properly. Sometimes it would run for a few seconds then die. The symptoms matched yours exactly, definitely sounded like an immobilizer bypass issue. Took it to my regular workshop where they diagnosed it as incorrect key programming. The car electronics system needed a reset and reprogramming of the key. Total repair cost was 45€ and took about an hour to complete. After that, no more starting problems. Before suggesting specific solutions, could you share: Does your security light stay on or flash? Have you had any recent work done on the car electronics? Are you using the original key or a spare? Does this happen with all keys you have? Knowing these details would help determine if your issue is similar to what I experienced with the key programming fault or if its something else in the immobilizer system.

Thanks for the detailed response and questions. My security light flashes when this happens and I'm using the original key, no spares. Haven't had any electrical work done recently, last service was at 18000km around 4 months ago. The fault seems to be getting worse over time. When it first started, the car would sometimes run for a minute before cutting out. Now it barely starts at all. Interesting to hear about your key programming fix, definitely sounds similar to what I'm experiencing with the ignition control issues. Did your mechanic mention if the immobilizer fault was causing any other electronic problems before you got it fixed?

The key programming issue definitely sounds similar, in my case the immobilizer fault also got progressively worse over time, just like yours. Before the fix, I noticed the central locking would sometimes act up too, which was apparently connected to the same car electronics module. The security light flashing with the original key is exactly what happened with my Golf. The immobilizer bypass system was essentially rejecting the key signal intermittently, even though it was the factory original. The mechanic explained that these anti-theft systems can develop glitches in the electronic handshake between the key chip and the car. One thing I should mention, before taking it to the workshop, I tried disconnecting the battery for 30 minutes hoping to reset the ignition control module. This actually made things worse and the car wouldn't start at all after that. Would recommend against trying any DIY fixes with the immobilizer system as it can complicate the reprogramming process. Since your symptoms are nearly identical and getting worse like mine did, you should probably get it checked soon before you end up completely stranded. The key reprogramming was a pretty straightforward fix once they had the right diagnostic equipment.

The diagnostics you shared are really helpful. The flashing security light and deteriorating performance match my symptoms perfectly. My central locking has actually started acting strange too this past week, I didnt connect the dots until you mentioned it, but it makes sense if its all tied to the same electronics module. Ill definitely avoid any DIY attempts with the immobilizer system based on your experience. Good to know about not disconnecting the battery, as I was actually considering trying that. The remote start feature hasnt been working properly either, which seems like another sign pointing to the anti-theft system having issues. Think ill book it in at a workshop this week while it can still start occasionally. Really appreciate you sharing your repair experience, helps narrow down the likely cause instead of just guessing. The key reprogramming solution seems the most logical fix given all the matching symptoms. Will report back on what the mechanic finds and whether it turns out to be the same ignition control module problem you had. Thanks again for the detailed insights.