O2 Sensor Malfunction Spikes Fuel Usage in S1 Model

Had the same issue on my A3 2013 with similar mileage. The check engine light came on due to a failing oxygen sensor heater element. The sensor testing revealed both a wiring harness problem and a degraded sensor unit in the exhaust system. The repair involved replacing the complete oxygen sensor assembly since the heater element was integrated. The faulty wiring harness also needed replacement due to damaged insulation near the connection point. This was a serious repair as it affected both fuel efficiency and emissions control. The symptoms matched exactly, increased fuel consumption and constant check engine light. Worth noting that driving with a faulty oxygen sensor can cause additional damage to the catalytic converter over time. Best approach is getting it fixed promptly as it affects the entire engine management system. The repair should include testing all sensor connections and replacing any corroded plugs while the system is opened up. After the fix, fuel consumption returned to normal and the engine management system worked perfectly again. Request testing of all sensor connections during repair to prevent future issues.

Thanks for sharing your experience. I had nearly identical symptoms with my S1 last winter. The malfunction indicator appeared right after regular maintenance, and vehicle emissions went out of spec according to diagnostics. Sounds like your repair process was thorough. Could you let me know what the total cost was for both the heater element and wiring repair? Also wondering if everything has stayed working properly since the fix. My mechanic suggested I might have additional sensor issues beyond just the oxygen sensor that need investigating.

Good news, after getting my A3 fixed, everything has worked flawlessly for months now. The faulty sensor issue turned out to be much simpler than initially suspected. Rather than needing a complete sensor replacement, the mechanic found and repaired a damaged cable connection to the oxygen sensor heater element. The repair cost was reasonable at 95 Euro, which covered diagnosing and fixing the defective plug connection. This was much better than replacing the entire sensor unit. The check engine light cleared immediately after the repair, and vehicle emissions returned to normal levels. The air-fuel ratio is now perfectly regulated, and fuel consumption has stayed at normal levels. Unlike your situation, I didnt need any additional sensor investigations. Considering your symptoms appeared after maintenance, it might be worth having them check if something was inadvertently disconnected during that service. The simple connection fix completely resolved all the symptoms, no more increased fuel consumption or warning lights. If your mechanic suspects multiple sensor issues, getting a second opinion might save you money before replacing components unnecessarily.

Just got back from the mechanic and wanted to share the outcome. The issue was traced to a damaged wiring connection near the oxygen sensor, similar to your case. The check engine light had me worried about expensive repairs, but it turned out simpler than expected. The mechanic found that during the last maintenance service, a wire near the exhaust system got pinched, affecting the heater element connection. Total repair cost was 120 Euro including diagnostic time. They fixed the wiring and tested the air-fuel ratio to confirm everything was working properly. Really glad I got this checked quickly. Fuel consumption is back to normal and the malfunction indicator finally cleared. No additional sensor problems were found, so it looks like the wiring was the only culprit affecting the emissions control system.