Audi A6 Turbo Performance Issues: Flashing CEL Alert

Had similar symptoms on a 2018 Audi A4 2.0T. The engine performance issues and turbo lag matched exactly what you describe. Diagnostic testing revealed a faulty vacuum switching valve, which was causing inconsistent boost pressure and affecting the bypass valve operation. The pressure sensor readings were unstable, indicating the turbocharger wasnt operating within normal parameters. This created noticeable compressor surge under acceleration. The root cause was a deteriorated diaphragm in the vacuum switching valve, preventing proper boost control. The repair required replacing the vacuum switching valve assembly and recalibrating the engine management system. While not a catastrophic issue, it needed immediate attention to prevent potential damage to the turbocharger system. Your symptoms strongly suggest a similar vacuum system issue. These problems typically worsen over time and can lead to more serious engine performance problems if left unaddressed. The repair process requires specialized diagnostic equipment to properly identify boost leaks and verify proper system operation. Focus on finding a shop with documented experience in VAG turbo systems, particularly with direct injection engines. Ask specifically about their diagnostic approach to boost-related issues.

Thanks for sharing your experience. I had almost identical issues with my A6 last summer, the flashing light and terrible turbo lag were really concerning. My boost controller also needed replacement along with the vacuum valve. Quick question, do you remember the total repair cost? Would help to compare with what I paid. Also curious if youve had any other boost-related problems since the fix?

Had the work done last month, total came to 140 Euro for replacing the defective vacuum switching valve. The boost pressure control fault cleared right up after the repair, and the turbo response is back to normal. The pressure sensor readings have been stable since then with no vacuum leaks detected. No issues since the fix was completed. The turbo lag is completely gone and fuel economy has returned to expected levels. The engine management system shows consistent boost pressure now, and the bypass valve is functioning as designed under all operating conditions. If youre seeing similar symptoms returning, a comprehensive pressure drop test would be worth doing to rule out any new vacuum system problems developing. These issues can sometimes indicate worn components elsewhere in the boost control system.

After dealing with multiple boost-related issues, I finally got it sorted at a specialized turbo shop last week. The mechanic found a significant vacuum leak and a failing boost solenoid that were causing the engine performance problems. Total repair came to 850 Euro including parts and labor. The diagnostic process was thorough, they pressure tested the entire system and found issues my previous shop missed. The engine performance is now back to factory specs. No more flashing lights or turbo lag, and my fuel economy has improved dramatically. Just wish I had gone to them first instead of wasting time with a general repair shop that lacked the right diagnostic tools. The specialized knowledge made all the difference in properly identifying and fixing the boost control system problems.