VW Lupo O2 Sensor Issues Impact Fuel Economy

Having dealt with a similar issue on my 2001 VW Polo diesel, I can share my experience. The malfunction indicator light also came on, and I noticed increased fuel consumption, which was concerning. The exhaust system includes oxygen sensors that monitor the air-fuel ratio, and when they fail, it often leads to these exact symptoms. In my case, after inspection, the workshop found a damaged wire connection to the oxygen sensor heater element. The repair involved replacing the wiring and connector assembly, which cost 95€ including labor. After the fix, fuel consumption returned to normal and the check engine light cleared. For a more accurate diagnosis of your specific case, could you share: Have you noticed any rough idling or hesitation during acceleration? What error codes exactly did you read? How long has the check engine light been on? Have you had any recent maintenance work done near the exhaust system? This information would help determine if your issue matches what I experienced with my Polo.

Last service was at 59000km. Before suggesting expensive parts replacement, I had my mechanic perform detailed sensor testing. The diagnostic revealed error code P0135, confirming the oxygen sensor heater circuit malfunction. Rough idle and sluggish acceleration were also present, along with the check engine light staying on constantly. My consumption went from 5.2L/100km to around 7L/100km overnight. The faulty sensor was indeed the culprit, causing the engine management system to run rich. After replacement, fuel economy improved and all symptoms disappeared. The part itself cost 180€ plus installation. Worth checking the wiring first though, as that could be a cheaper fix if you have a connection issue rather than a failed sensor.

Thanks for providing those details about your experience. Similarly with my Polo, after seeing error code P0135 during sensor testing, I initially hoped it was just a wiring issue like in my previous repair. However, this time the oxygen sensor itself had failed. The symptoms match exactly, my fuel consumption also jumped from about 5.5L/100km to over 7L/100km. The malfunction indicator came on because the air-fuel ratio was running too rich without proper feedback from the sensor. I ended up paying 175€ for the part plus labor. While checking connections is smart, in my case the complete sensor replacement was unavoidable. The vehicle emissions returned to normal levels after fixing it. Since your Lupo shows identical symptoms and the same error code as what I experienced, a faulty sensor seems likely. The exhaust system components between our models are very similar. Just make sure your workshop performs proper sensor testing to confirm its not just a loose connection before replacing the full unit.

Thanks for all the feedback and suggestions. Your experiences with similar sensor issues really helped confirm my diagnosis. After having it properly tested and seeing that same P0135 code related to the heater element, I went ahead with the full oxygen sensor replacement. Like your cases, the vehicle emissions and fuel consumption were clearly affected by the faulty sensor. The repair cost was about what I expected at 180€ for the part plus labor. The car components around the exhaust system all checked out fine, it was definitely just the sensor causing problems. Most importantly, the car is running perfectly again. Fuel consumption is back to normal at 5.2L/100km and the check engine light has stayed off. While I initially hoped it might just be a wiring issue, replacing the complete sensor was the right call. The thorough testing definitely helped avoid any guesswork with the repair. Thanks again for helping me understand what I was dealing with. Your detailed descriptions of the symptoms and repair process gave me confidence in getting it fixed properly.