VW Lupo Won't Start: Immobilizer System Failure Alert

Having some experience with VW electronics, I faced a very similar issue with my VW Polo 1.9 TDI from 2002. The symptoms match exactly what you describe, engine cutting out and security light illuminating, which pointed to the car immobilizer system. The anti-theft system was preventing the engine from running due to incorrect key programming. The remote start function would work briefly, but then the immobilizer would kick in and shut everything down. After some failed attempts at fixing it myself, I took it to a workshop specializing in ignition control systems. The diagnostic revealed that the key needed reprogramming to properly communicate with the immobilizer. The repair was straightforward, they used specialized equipment to sync the key with the car's security system. Total cost was 45€ and the problem never returned. Before suggesting specific solutions for your case, could you provide: Complete engine code, Type of key you are using (original or replacement), When the problem first started, Any recent work done on the electrical system, Whether you have a spare key to test This information would help determine if your issue is identical to what I experienced with my Polo.

Last service done at 117000km, so the symptoms are likely not maintenance related. The key programming suggestion sounds promising. When testing with my spare key, I notice the same behavior, both keys trigger the security light. This seems to confirm the anti-theft system is the root cause rather than a mechanical issue. Before I take it to a specialist, would clearing the immobilizer fault codes with a scan tool be worth trying? Or could this potentially make the ignition control issue worse? Just want to avoid complicating the repair further. Also checked and mine is the original VW key with the black plastic head, not an aftermarket replacement. Haven't had any electrical work done recently that could have triggered the car immobilizer malfunction.

Thanks for providing those details about your keys and service history. Your symptoms match my Polo situation even more closely now, especially with both original keys showing the same behavior. I would strongly advise against clearing the immobilizer fault codes yourself. When I attempted this on my Polo, it actually complicated the key programming process later. The anti-theft system is quite sensitive, and improper reset attempts can cause the immobilizer bypass procedure to be more complex and expensive. The fact that both your original keys trigger the security light points clearly to an issue with the immobilizer control module rather than the keys themselves. On my car, the workshop found that the module needed recalibration in addition to key programming. A proper fix will likely require: Professional diagnostic scan, Immobilizer module testing, Key signal verification, Complete system reprogramming The total repair cost should be between 100-200€ depending on whether the module needs replacement. While this might seem high, attempting DIY solutions with the car electronics could lead to a permanently locked immobilizer, which would be far more costly to resolve.

Thanks for the detailed advice. I know I definitely need professional help with this now! After hearing about your experience, I wont risk messing with the immobilizer fault codes myself. Makes total sense that DIY attempts could make the anti-theft system problems worse. The symptoms match your Polo case exactly, both original keys triggering the security light and the engine cutting out. Good to know the fix involved both the immobilizer module and key programming. The 100-200€ cost estimate helps set my expectations for the repair. Will look for a workshop that specializes in VW security systems and key signal issues. Better to get it done right the first time than risk damaging the immobilizer control module with amateur attempts at bypassing it. Really appreciate you sharing your experience, saved me from potentially making the problem much more expensive to fix. Will get it booked in ASAP since I need the car running reliably again.