CTS Won't Start: Security System Blocks Engine Start

I faced a similar ignition control issue with my 2012 Cadillac ATS. With some experience working on cars, I recognized the symptoms matched a car immobilizer problem. The security light behavior and starting issues pointed to the key signal not being properly recognized. My local workshop diagnosed it as incorrect key programming, which was causing the immobilizer fault. The fix involved reprogramming the key to properly communicate with the immobilizer system. The repair took about an hour and cost 45€. Since then, the remote start and security systems have worked flawlessly. The workshop mentioned this is fairly common in this model range. To better assist with your specific situation, could you share: Does the problem occur with all keys? When did these symptoms first appear? Have you recently replaced or reprogrammed any keys? Are there any other electrical issues present? What error codes exactly did your scan reveal? This information would help determine if your issue matches what I experienced or if it might be something different.

Thanks for sharing your experience. Similar symptoms on my CTS with 69327 KM. Initially suspected a dead battery but after the scan showing immobilizer system codes, it seems more complex. The anti-theft system appears to be the culprit based on your description. The security light behavior matches exactly what you described. Both my original keys exhibit the same issue, which started happening after my last service about 2 weeks ago. No recent key programming or replacements done. The error codes point to an immobilizer bypass malfunction, suggesting the system fails to authenticate the key signal properly. Would you recommend going straight for key reprogramming or should I get a full diagnostic first?

Based on both keys showing the same symptoms after a recent service, this seems different from my ATS case. While the security light behavior is similar, having it affect both keys right after service suggests potential interference with the anti-theft system during maintenance. With my experience, I would strongly recommend getting a full diagnostic first. The timing of the issue starting after service could indicate technician-induced problems with the immobilizer system or its wiring. When my ATS had issues, it was limited to one key, making key programming the obvious fix. The error codes you mentioned about the immobilizer bypass malfunction could also point to: Damaged wiring from the service work, Accidental disconnection of ignition control components, Issues with the anti-theft system module itself In my case, a simple key programming fixed everything for 45€. However, given your situation started after service, you might want to: 1. Return to the service center to check if anything was disturbed 2. Get a proper diagnostic scan focused on the security system 3. Consider having a professional check the wiring integrity This could save you from paying for unnecessary key programming if the root cause lies elsewhere in the system.

Thanks everyone for the input. After reading about your experiences, I will take my CTS back to the service center first. Since the car immobilizer issues started right after their work, they should at least check if something was disconnected or damaged during the service. If they dont find anything obvious, I will have them do a full diagnostic of the anti-theft system before attempting any key programming. The security light behavior and starting problems affecting both keys does suggest this could be more than just a key issue. Will update once I know what caused the immobilizer fault. Really hoping its just a loose connection from the service work rather than needing a more expensive fix to the security system. Appreciate all the detailed advice on how to approach this systematically rather than jumping straight to key reprogramming.