Audi A1 Immobilizer Fault Causes No-Start Mystery

Had a similar issue with my 2019 Audi A3 last winter. With some experience working on Audi electronics, I recognized this as a classic key programming problem affecting the immobilizer system. The symptoms matched exactly, dashboard lit up normally but engine would not stay running, suggesting the immobilizer was not properly releasing. After checking the basics like battery and fuel, took it to an authorized workshop specializing in car immobilizer systems and key programming. Turned out the transponder chip in the key needed reprogramming to properly communicate with the anti-theft system. The entire process took about an hour and cost 45 Euro. Since the fix, the car has started perfectly every time. Before suggesting specific solutions, could you share: Have you tried using your spare key? Are there any other warning lights besides check engine? What specific error codes are stored? Has any recent work been done involving the electrical system? This would help determine if your issue is identical to what I encountered or if there might be additional factors involved with your remote start system.

My car has 56947 KM and had its last service 3 months ago. No electrical work was done during that maintenance. I tried both the main and spare key but getting the same result. Besides the check engine light, there is also a flashing immobilizer symbol on the dash. The stored error codes are P1634 and P1570, which seem related to the ignition control unit communication. The diagnostic readout suggests a fault in the signal exchange between the key transponder and the car immobilizer system. No recent electrical work has been done that could have triggered this. Really hoping this can be resolved with just key programming rather than replacing the entire ignition control module.

Thanks for the additional details, those error codes match what I encountered on my A3 before getting it fixed. P1634 and P1570 are definitely immobilizer-related and point to communication issues between the key and the security system, just like in my case. Since both keys show the same symptoms and you have the flashing security light, I'm more convinced this matches my situation where the immobilizer system lost its programming. The ignition control unit is likely fine since it's recognizing the key presence but failing the authentication step. In my repair, they did not need to replace any hardware. The workshop performed a complete immobilizer bypass and reprogramming sequence that restored proper communication. The total repair ended up around 180 Euro including diagnostic time, notably less expensive than replacing modules. Based on the matching symptoms and error codes, I would recommend taking it to a shop that specializes in car immobilizer systems rather than a general service center. They will have the proper diagnostic equipment to reset and reprogram the anti-theft system.

The advice about specialized immobilizer system repair seems spot on. Just contacted a local auto electronics specialist who confirmed they frequently handle these exact error codes with Audi models. They quoted 200 Euro for full diagnostic and reprogramming service, which sounds reasonable compared to the cost of replacing the ignition control module. Will book the car in next week and update once I know if a simple key programming resolves the security light and starting issues. Really hoping the immobilizer fault can be fixed through reprogramming like in your case, as replacing hardware would be much more expensive. The matching error codes and symptoms are encouraging that this might be a straightforward fix. Appreciate the detailed information about your experience, particularly helpful to know that no parts replacement was needed in a similar situation. Will post back with the results after the repair attempt.