Faulty Sensor Cripples RS7's Twin-Turbo Performance

I had a similar issue with my RS6 from 2012 with the same 4.0L engine. With some experience working on performance cars, I can relate to your symptoms. The engine management system was indeed putting my car into limp mode due to an exhaust leak near the temperature sensor. The workshop found that the exhaust gasket had deteriorated, causing false readings from the heat sensor. This triggered the engine protection mode, resulting in power loss and increased fuel consumption. The repair involved replacing the faulty exhaust gasket and a preventive replacement of the temperature sensor, as it had been affected by the leak. Total cost was 265 Euro including parts and labor. The car has been running perfectly since the fix. To help diagnose your case more precisely, could you share: Current mileage, Any unusual sounds from the exhaust system, Whether the check engine light is constant or intermittent, If you notice any exhaust smell in the cabin These symptoms often point to exhaust sensor issues, but proper diagnosis through a diagnostic tool would confirm if the temperature sensor is actually the culprit.

Thanks for your reply and the detailed information. My current mileage is 45214 KM and the last service was done 2 months ago. The check engine light is constantly on, not flickering. No unusual smells in the cabin, but I notice the temperature fluctuation on cold starts. After reading your experience, I checked with a diagnostic tool and it confirmed the exhaust sensor fault code. The sensor replacement might indeed solve the power loss issue. Good to know the repair costs were reasonable in your case. Our cars seem to share similar temperature sensor problems despite being different models. Will schedule a workshop visit to have the engine management system properly checked and the sensor replaced if needed.

The temperature fluctuation you mention on cold starts is exactly what I experienced before my repair. Since we have the same engine platform, these symptoms are quite telling. The exhaust sensor in these 4.0L engines is particularly sensitive to temperature changes, and a faulty one can definitely trigger the engine management system to reduce power. After my sensor replacement, I noticed the cold start behavior returned to normal, no more temperature fluctuation on the readouts. The exhaust components in our cars are designed to work within precise parameters, and when the temperature sensor starts failing, it affects the entire system performance. One tip from my experience: have them inspect the surrounding exhaust components while replacing the sensor. In my case, they found minor wear on nearby gaskets that could have caused issues later. The preventive replacement saved me from future problems. The constant check engine light you describe matches my situation perfectly. If the diagnostic tool showed the exhaust sensor fault code, you are likely dealing with the same issue I had. The repair should resolve both the power loss and fuel consumption problems you are experiencing.

With 45214 KM and issues showing up now, your insights about similar sensor problems across these engines is helpful. The diagnostic code definitely supports what you found with your RS6 repair. After discussing the symptoms, I am confident the exhaust component inspection and sensor replacement will fix my issues. The temperature fluctuation during cold starts matches what you experienced before your repair. Will take your advice about checking surrounding parts during the sensor replacement. Making sure all exhaust system components are in good condition makes sense, especially considering the age of these cars. The engine management problems and constant check engine light should be resolved once the faulty sensor is replaced. Will schedule the repair this week and have them do a thorough inspection while they are working on it. The repair costs you mentioned give me a good baseline for what to expect. Appreciate the detailed explanation of your experience, it helped confirm my suspicions about the temperature sensor being the root cause.