Touareg O2 Sensor Issues: High Fuel Use Warning Signs

Had a similar issue with my 2018 Tiguan Hybrid last winter. The check engine light came on and fuel efficiency dropped noticeably. After checking error codes, the symptoms matched your description exactly. The workshop diagnosed a faulty connection in the oxygen sensor wiring harness. The cable insulation had worn through, causing inconsistent air-fuel ratio readings. Total repair cost was 95€ including diagnostics and fixing the connection. No need to replace the entire sensor in my case. The repair completely resolved both the check engine light and fuel consumption issues. The car runs perfectly since then. To help diagnose your specific case, could you share: What error codes came up in the scan? Have you noticed any other symptoms like rough idling or hesitation? Is the check engine light steady or flashing? When did you last have routine car maintenance done? This information would help determine if your issue is similar to what I experienced or potentially something different. While oxygen sensor issues are common, proper diagnosis is important before replacing parts.

Latest maintenance was at 98000km. The error codes showing are P0171 and P0174, which point to a lean fuel mixture. The check engine light stays steady, no flashing. No rough idling, but definitely feeling some hesitation during acceleration. I appreciate the insight about checking the wiring harness. That could explain the erratic exhaust system readings Im seeing. The repair cost you mentioned is much lower than the 450€ quote I received for a complete O2 sensor replacement. Good point about proper diagnosis. Ill have them inspect the wiring connections first before committing to replacing the entire automotive sensor assembly. The air-fuel ratio issues could definitely stem from damaged wiring rather than a failed sensor.

Thanks for providing those error codes, P0171 and P0174 are indeed classic indicators of a lean condition, quite similar to what I experienced. In my case, the damaged wiring was causing incorrect air-fuel ratio readings, but after fixing just the wiring, the sensor started working perfectly again. One additional detail from my repair that might help: the technician found the wiring damage was actually near the connection point where the exhaust sensor harness meets the main loom, not at the sensor itself. This area tends to get overlooked during routine car maintenance. Since youre experiencing hesitation during acceleration, which I also had, it really strengthens the case for a wiring issue rather than complete sensor failure. The steady check engine light also matches my experience, a failing catalytic converter typically causes a flashing light. The 450€ quote does seem high if its just wiring. Maybe ask them specifically to inspect the harness connections first, focusing on wear points near heat shields and mounting brackets. That could save you significant money while properly addressing the root cause in the exhaust system.

Perfect timing with those error codes you shared, P0171 and P0174 match exactly what I was seeing during my fuel mixture issues. Makes sense about the steady check engine light too, and hearing about your experience with the wiring harness versus full sensor replacement is super helpful. The hesitation during acceleration at 98000km definitely tracks with my symptoms. After getting that repair quote of 450€ for a complete oxygen sensor swap, Im glad I posted here first. Going to request a full wiring inspection, especially around the exhaust system connection points you mentioned, before agreeing to any parts replacement. Really helpful info about how wiring damage can mimic a bad automotive sensor. Will get them to do a thorough check of the harness near the heat shields and mounting points during the next car maintenance visit. Much rather pay for a wiring fix than spring for unnecessary catalytic converter or sensor replacements if the core issue is just a damaged connection. Thanks for the practical advice, saved me from potentially overpaying for parts I might not even need.