A8 AdBlue System Failure Prevents Engine Start

I had a similar issue with my 2019 A7 diesel last winter. Having some experience with diesel exhaust systems, I initially thought it was just low AdBlue fluid, but the problem turned out to be more complex. The dashboard alert showed emission control system warnings, and the service light came on simultaneously. After checking the AdBlue tank level manually, which was actually sufficient, I took it to a workshop. They diagnosed a faulty connection between the AdBlue tank and the dosing unit, which was preventing proper fluid transfer to maintain emission standards. The repair took about 4 hours, and the total cost was 250 Euro, including parts and labor. The fuel efficiency remained unaffected after the fix, but its crucial to address these issues promptly to prevent potential damage to the SCR system. What engine variant does your A8 have? Also, can you share the specific error codes? This would help determine if youre dealing with the same component failure. The repair approach might differ based on the exact configuration. A warning: dont attempt to drive the vehicle extensively with active SCR system errors, as this could lead to more expensive repairs.

Latest service was at 152000km. The error codes are P20E8 and P20EE. My SCR catalyst seems to be working normally according to the diagnostic report from last week, but the injection system still shows intermittent faults. The tank capacity for AdBlue is sufficient at 75%, so fluid level isnt the problem. The workshop quoted 850 Euro for a complete diagnosis and potential replacement of the dosing module. This seems quite steep considering the car is still relatively new. Has anyone managed to resolve similar issues with just a software update or cleaning of the injection system?

Thanks for the additional details. On my A7, those exact error codes initially appeared after a cold start period. Based on the symptoms you describe and the diagnostic report showing adequate SCR catalyst function, this points strongly toward the dosing module rather than a broader emission control system issue. The 850 Euro quote seems high compared to my repair, but if the dosing module needs replacement rather than just the connection fix I had, its actually in line with current parts pricing. A software update alone probably wont resolve it, in my case, they tried that first without success. With the AdBlue injection system showing intermittent faults despite normal fluid levels, the symptoms match what I experienced before the dosing unit was repaired. The service history at 152000km is recent enough to rule out maintenance-related causes. Consider requesting a detailed breakdown of the quoted repair costs. The workshop should explain why they believe the entire module needs replacement versus repairing connections or cleaning the system. For reference, the cleaning service for the injection system typically costs around 200 Euro, but given the error codes, this might only be a temporary fix. The service light will likely stay on until the dosing module issue is properly addressed, and continuing to operate the vehicle could impact emission standards compliance.

The codes P20E8 and P20EE with my mileage indeed match their diagnosis. After checking in depth, my service records actually show a previous AdBlue consumption rate change just before these issues started. The 850 Euro repair quote breaks down to 650 Euro for the dosing module and 200 Euro for labor, which aligns with current market rates based on feedback here. The injection system continues showing the same faults, and the service light remains on despite multiple restarts. The emission control system warnings are consistent, confirming what others experienced. While waiting for the repair slot next week, Ive kept the vehicle usage minimal to prevent potential damage to the SCR catalyst. Ill proceed with the module replacement since a simple software update or cleaning likely wont fix these specific error codes. The workshop confirmed they can complete the repair in one day, which should restore proper AdBlue delivery and bring the system back to meeting emission standards. The dashboard alert should clear once the new dosing module is installed and calibrated.