Audi Q2 AdBlue System Prevents Engine Start

Had the same issue on a 2016 Audi Q3 2.0 TDI. The emissions control system showed similar symptoms, but the DEF fluid level was actually full. The problem turned out to be a faulty dosing module in the injection system, not an empty tank. The service light indicated an SCR system malfunction, and the engine refused to start after several warnings. This is a serious issue because the emissions control system will eventually shut down the engine completely to protect the catalytic converter. The repair required replacing the complete dosing unit, as the DEF fluid was crystallizing inside the lines due to a pump malfunction. The diesel exhaust system needs this component to work perfectly to maintain proper emissions levels. Key points to check: Verify if DEF fluid level sensor is working correctly, Check for crystallization in the AdBlue lines, Have the dosing module tested, Get the injection system pressure tested This is a common failure point on VAG diesel models from that generation. Would suggest going to a workshop that specializes in diesel exhaust systems, as general mechanics often misdiagnose these symptoms.

Yes, I had that exact problem with my Audi Q2 earlier this year. The dashboard alert kept showing the SCR system error and the car refused to start after several warning messages. My DEF fluid levels were fine but the service light stayed on. Like you mentioned, the stored error code pointed to the AdBlue system. After a proper diagnosis, it turned out the emissions control system had a failing sensor, not the complete dosing module. The repair was much simpler than expected. Do you remember the repair costs for your case? Also curious if you experienced any related issues since getting it fixed? My diesel exhaust system has been running perfectly after the sensor replacement, but always good to know what to watch out for.

Thanks for asking about the follow-up. After seeing a specialist workshop about the AdBlue issue, they found the connection from the tank to the dosing unit was indeed defective. The repair cost came to 250 Euro, which included fixing the faulty output and resetting the injection system warnings. Since the repair, my diesel exhaust system has been working flawlessly. The fuel efficiency actually improved slightly after the fix, likely because the SCR catalyst system is now operating at optimal levels. No more dashboard alerts or DEF fluid related warnings have appeared. The specialist confirmed that maintaining proper flow from the AdBlue tank to the dosing unit is crucial for the emissions control system to function correctly. If the connection fails, it can trigger the same symptoms even when the tank is full. Worth noting that regular DEF fluid level checks are still important, but in our cases, the issue clearly stemmed from component failure rather than fluid levels.

After taking my Audi to a certified diesel specialist, they found and fixed the faulty sensor in under 2 hours. The total repair cost was 180 Euro, much less than I expected after seeing the alarming dashboard alerts. The mechanic showed me exactly where the sensor had failed in the SCR catalyst system. They also performed a complete system check to ensure no other components were affected. The fuel efficiency has remained stable since the fix, and the service light hasnt returned. The most frustrating part was my previous mechanic missing this simple diagnosis and suggesting a full system replacement. Finding a workshop that actually specializes in diesel exhaust systems made all the difference. For anyone facing similar emission standards compliance issues, getting a proper diagnosis from a diesel specialist is definitely worth it.