VW Touran O2 Sensor Issues Cause High Fuel Usage

I had a similar situation with my VW Golf from 2014 with a gasoline engine. As someone with some car repair experience, particularly with exhaust system components, I can share my experience. The symptoms matched exactly what you describe, the check engine light, increased fuel consumption, and the error codes pointing to the oxygen sensor. The faulty sensor was causing incorrect air-fuel ratio readings, leading to the engine running rich. After inspection, my mechanic found that the heater element connection was loose, causing intermittent failures. The cable connection to the oxygen sensor had deteriorated over time. Rather than immediately replacing the entire sensor, they first checked all connections thoroughly. The repair involved fixing the wiring and plug connection, which solved the issue completely. The total cost was 95€ for diagnostic work and repairing the connection. This was much cheaper than replacing the entire sensor unit. After the fix, fuel consumption returned to normal levels and the check engine light stayed off. Before suggesting specific solutions, could you share: The exact error codes you received, Your current mileage, Whether you notice any other symptoms like rough idling, Have you had any recent exhaust system work done This information would help determine if your issue is similar and whether the same solution might work.

Latest service was done at 42000km and they found no issues. The error code I got was P0141. Besides the mentioned symptoms, I also noticed occasional stuttering during acceleration. The exhaust system has had no work done on it since I bought the car. Looking at the vehicle emissions data from the onboard computer, fuel efficiency dropped from 7.2L/100km to about 8.5L/100km after these issues started. Testing the oxygen sensor output voltage seems to confirm inconsistent readings, especially when the engine is warming up. Would checking the wiring connections first be a good starting point before replacing the sensor completely?

Thanks for providing those details. In my Golf, I also had the P0141 code, and the stuttering during acceleration is a telltale sign I experienced too. The jump in fuel consumption from 7.2 to 8.5L/100km matches almost exactly what I saw before fixing the issue. The wiring check is definitely the smart first step. In my case, the vehicle emissions were affected due to poor connections rather than a completely faulty sensor. The oxygen sensor testing showed similar inconsistent voltage readings during warm-up, but the sensor itself was actually fine. When my mechanic inspected the wiring, they found corrosion at the connector pins and a slightly loose harness connection. After cleaning the connections and securing the harness properly, the sensor started working correctly again. The stuttering disappeared completely and fuel economy went back to normal within two tank fills. If the wiring check shows no issues, then sensor replacement might be necessary. But given your symptoms are so similar to what I experienced, checking the connections could save you the cost of a new sensor. The diagnostic and wiring repair cost is typically much lower than replacing car components unnecessarily. Would you be able to verify if the connector near the sensor shows any signs of corrosion or damage? This could help determine if you have the same root cause.

Based on what you both shared about the oxygen sensor issues, I will definitely check the wiring connections first. The voltage readings I am getting match your experience exactly, and since the repair costs were much lower for fixing connections versus replacing the entire sensor, this seems like the logical first step. I just checked the connector area near the oxygen sensor and noticed some dark spots that could be corrosion. Given that my air-fuel ratio issues and increased fuel consumption mirror what you experienced with your Golf, I am hopeful this might be the root cause. The exhaust system has been exposed to all kinds of weather conditions over the years, so connector corrosion makes sense. I will have my mechanic inspect the wiring and clean the connections before considering a full sensor replacement. The check engine light and stuttering during acceleration are annoying, but at least there is a good chance of an affordable fix. Will post an update once I get the wiring checked and know if this resolves my vehicle emissions problems. Thanks for sharing your detailed repair experience, it likely saved me from unnecessarily replacing an expensive part.