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ninabauer1

S6 O2 Sensor Issues Causing High Fuel Consumption

Check engine light on

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Poor fuel economy

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Fault stored

Recently my 2013 Audi S6 started acting up with increased fuel consumption and a persistent check engine light. The error scan shows a malfunction indicator related to what appears to be the O2 sensor heater element. Before taking it to a workshop, I would like to understand if anyone has dealt with similar symptoms and can share their repair experience. Was sensor testing enough to confirm the issue? Looking for insight into what repairs were needed and if it actually solved the elevated fuel consumption problem. Also interested in knowing if the air-fuel ratio returned to normal after fixing the faulty sensor.

4 comment(s)


florian_vogel7

I had a very similar issue with my 2015 Audi S4. With some experience working on cars, I can share how this situation played out for me. The symptoms matched exactly what you describe, high fuel consumption and check engine light. After sensor testing confirmed the oxygen sensor malfunction, I discovered it was actually just a damaged wiring connection to the sensor rather than the sensor itself being faulty. The repair involved fixing the cable and plug connection to the O2 sensor, which cost 95 Euro. After the repair, fuel consumption returned to normal levels and the check engine light cleared. The vehicle emissions and air-fuel mixture normalized once the sensor was receiving proper electrical input again. Before suggesting more specific advice, could you share: Have you noticed any rough idling? Does the check engine light flash or stay constant? Are you experiencing any power loss during acceleration? What are your current fuel consumption numbers? This information would help determine if your situation truly mirrors what I encountered with my S4 or if there might be other factors to consider.

ninabauer1 (Author)

My car has 154751 KM on the clock, and while I appreciate the advice about wiring connections, my case seems different. After reading up on related issues, the symptoms point more towards a complete failure of the heater element within the O2 sensor assembly. The exhaust system shows normal operation otherwise, but the persistent malfunction indicator suggests this faulty sensor is affecting the engine management. Beyond the fuel consumption, I am now also noticing slight hesitation during cold starts, which further aligns with common heater element failures in these specific car components. I will have the sensor tested comprehensively before replacement to ensure we identify the exact issue. Has anyone else seen cold start problems develop alongside these sensor readings?

florian_vogel7

Based on what youre describing, especially the cold start issues, it definitely sounds like a failing O2 sensor heater element rather than just wiring. With my S4, I initially thought the wiring fix would solve everything, but I eventually had to replace the entire sensor unit a few months later when similar cold start problems emerged. The car components involved in the O2 sensing system are quite sensitive to temperature variations. When I finally replaced the sensor, both the hesitation during cold starts and the high fuel consumption issues were fully resolved. The vehicle emissions returned to normal levels and the malfunction indicator finally stayed off permanently. After dealing with this on my S4, I learned that degraded heater elements often show these progressive symptoms, starting with general performance issues and eventually affecting cold start behavior. The comprehensive testing you mentioned is a smart approach. When I had mine tested, the readings clearly showed the heater element was not reaching proper operating temperature. For reference, the complete sensor replacement ended up costing 285 Euro including labor, but it was worth every cent considering the improved performance and normalized fuel economy. Would be interested to hear what your testing reveals, as these issues can sometimes be tricky to diagnose definitively.

ninabauer1 (Author)

Thanks for all the input regarding the O2 sensor problems. After reviewing the suggestions and comparing them with my symptoms, I feel more confident about moving forward with the testing and likely replacement of the sensor. The cold start issues combined with the consistent malfunction indicator and increased fuel consumption really do point toward a failed heater element in the O2 sensor. Will schedule comprehensive sensor testing this week to confirm the diagnosis before proceeding with the replacement. With 154751 KM on my S6, it makes sense that these components might need attention. While the 285 Euro repair cost mentioned is significant, restoring proper air-fuel ratio and reducing fuel consumption would make it worthwhile. The check engine light has been quite persistent, and addressing this properly should help maintain optimal vehicle emissions and performance. Will update once I have the test results and know more about the exact nature of the sensor malfunction. Really hoping this resolves both the cold start hesitation and the fuel economy issues.

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