Audi Q3 AdBlue Issues Cause Complete Engine Shutdown

Having dealt with a very similar issue on my Audi Q5 2.0 TDI (2016), I can share my experience as someone with moderate technical knowledge of diesel engines. The symptoms match what I encountered, multiple warnings followed by complete engine shutdown. While an empty DEF fluid tank can trigger warnings, it usually provides advance notifications. In my case, the actual problem was the connection between the AdBlue tank and the dosing unit. The issue prevented proper DEF fluid flow to the SCR catalyst, causing the engine management system to shut down, a common safety feature to protect the emission control system. The service light appeared first, followed by multiple system warnings. The repair involved: Complete diagnostic scan, Cleaning of the delivery unit, Replacement of the faulty dosing module, System reset and calibration Total cost was 250 Euro including parts and labor. The fuel efficiency returned to normal after the fix, and the service light cleared immediately. Before suggesting specific solutions, could you provide: Current DEF fluid level reading, Complete error codes if available, Approximate mileage since last AdBlue refill, Any unusual sounds or behavior before the shutdown This information would help determine if your issue matches the common dosing unit failure pattern or indicates a different problem with the injection system.

Thanks for the detailed response. I should mention my car has only 7522 KM and had its last service 2 months ago. The technician checked all emission control systems during that service. Before the complete shutdown, I noticed the dashboard alert for the SCR catalyst was flashing briefly. The DEF fluid level sensor might be faulty since it showed full just days before these issues started. The car ran perfectly fine until yesterday morning when all these warnings suddenly appeared. The injection system seems fine based on how smoothly the engine ran before stopping. I will try to get the error codes read tomorrow. Would measuring the actual DEF fluid level manually help diagnose the issue?

Thanks for providing those additional details. The low mileage on your Audi makes dosing unit failure less likely compared to my case. However, the combination of SCR catalyst alerts and sudden shutdown still follows a similar pattern. Manual DEF fluid level checking would definitely help diagnose the issue. On my Q5, the actual fluid level turned out to be different from the sensor reading, pointing to a sensor malfunction rather than a delivery problem. The situation with your car has some key differences from what I experienced: Much lower mileage, Recent service verification, Sudden onset vs gradual warning progression, Possible sensor malfunction rather than delivery issue Based on these factors and the diesel exhaust system inspection during your recent service, I suspect this could be an electrical issue affecting the DEF fluid monitoring system rather than a mechanical problem. In my experience, sudden complete failures often point to sensor or control unit malfunctions. Getting the error codes read should be the next step, it will show if the system is detecting a true DEF fluid issue or responding to incorrect sensor data. When my dosing unit failed, the diagnostic scan showed specific SCR system fault codes that helped pinpoint the problem. Keep us updated with the error codes. The solution might be simpler and less costly than my repair if it turns out to be just a sensor issue.

Thanks for sharing your case, I really appreciate the additional information about sensor issues versus delivery problems. It helps narrow down my situation. Since my car was just serviced and the issue came on so suddenly, your insight about electrical problems makes sense. The dashboard alert pattern matches what you described with your sensor malfunction rather than the gradual warnings typical of an empty tank. I will check the actual DEF fluid level manually tonight and have the error codes read tomorrow. The fact that your diagnostic scan pointed to specific SCR system codes gives me hope this can be properly diagnosed. My concern about a complete injection system failure seems less likely given the circumstances. Will definitely update once I have the error codes. The service light is still on but at least knowing this might be a sensor issue rather than a major mechanical problem with the emission standards system is somewhat reassuring. Looking forward to comparing the diagnostic results with your experience. Did your repair center mention any specific testing procedures they used to confirm it was the sensor before starting repairs?