VW Jetta Hybrid O2 Sensor Issues Causing High Fuel Use

As someone with moderate experience working on VW hybrids, I encountered a similar issue with my 2017 VW Passat GTE. The symptoms you describe match what I experienced, higher fuel consumption and an illuminated check engine light. The air-fuel ratio was off due to a faulty cable connection at the oxygen sensor. After proper car maintenance checks, my mechanic found the plug connection had worked loose over time, affecting the sensor readings and overall exhaust system performance. The repair was straightforward, they cleaned the connection points and secured the plug properly. Total cost was 95€ for diagnostic work and fixing the connection. Much cheaper than replacing the entire oxygen sensor or checking the catalytic converter. Before suggesting specific solutions, could you share: Current mileage on your Jetta, Any other warning lights or unusual behavior, Whether fuel consumption increased gradually or suddenly, If you notice any exhaust smell or unusual engine sounds This information would help determine if your issue matches what I experienced or if further investigation is needed.

Thanks for the input. Regarding my Jetta's details, last service was completed at 98000km and current mileage is now at 102392km. The fuel consumption increased quite suddenly over the past 2 weeks. I am getting around 2L/100km more than usual. No unusual smells from the exhaust system, but there is a slight rattling noise when accelerating. The O2 sensor reading seems unstable according to my OBD scanner. After checking multiple connections, I did notice the exhaust sensor wiring appears slightly corroded near the connector. This could explain the erratic readings affecting fuel efficiency. Going to have my mechanic take a closer look at the wiring before replacing any automotive sensors.

Thanks for those additional details. Your symptoms sound very familiar to what I experienced with my Passat GTE, especially the sudden increase in fuel consumption and unstable O2 readings. The corroded wiring you found near the exhaust sensor connector is likely the root cause. In my case, the corrosion had spread inside the connector, causing inconsistent air-fuel ratio readings. This matches your OBD scanner results showing unstable readings. The rattling during acceleration was also present in my car, it turned out to be related to the system running a richer fuel mixture due to incorrect sensor data. After cleaning the connections and replacing the corroded section of wiring (around 150€ for parts and labor), my fuel efficiency returned to normal within a few days. Given your mileage and the sudden onset of issues, I would strongly recommend having your mechanic: 1. Clean all sensor connections 2. Replace any corroded wiring sections 3. Check the sensor ground points 4. Perform a complete system reset after repairs The car maintenance cost should be significantly less than replacing the entire oxygen sensor unit. Based on your description, the automotive sensor itself is likely still functional, its just getting poor electrical connections due to the corrosion.

Based on your thorough inspection and analysis, I think we are definitely on the right track focusing on the wiring issue. The similarities with your Passat GTE case are really helpful, especially regarding the sudden fuel consumption increase and unstable readings. I scheduled an appointment with my mechanic for next week. Will have them thoroughly check all the exhaust system connections and wiring, particularly around that corroded section near the O2 sensor. The estimated 150€ repair cost for cleaning and replacing affected wiring seems much more reasonable than what I initially feared. The air-fuel ratio issues make sense given the symptoms, and I am hopeful cleaning the connections and replacing the corroded wiring will resolve both the check engine light and fuel consumption problems. Will start tracking fuel efficiency right after the repair to confirm the fix worked. Thanks for sharing your experience, it saved me from potentially replacing a perfectly good automotive sensor. Will update once the repair is complete to confirm if this resolved the issue for future reference.