VW Passat Hybrid O2 Sensor Issues Impact Performance

I had a very similar issue with my 2020 VW Golf Hybrid last winter. As someone with moderate experience in car maintenance, I initially tried sensor testing myself using a basic OBD reader. After getting multiple error codes related to the exhaust system and air-fuel ratio, I decided to take it to a workshop. The malfunction indicator kept lighting up, and the fuel economy was terrible, just like your case. The mechanic diagnosed a loose connection in the oxygen sensor wiring harness. The cable connection to the sensor was damaged, causing incorrect readings. Total repair cost was 95€, which included diagnostic testing and fixing the faulty sensor connection. Before you proceed with repairs, could you share: The specific error codes from your diagnostic scan, Whether the check engine light is constant or intermittent, If you notice any unusual exhaust smell or noise, The approximate mileage of your vehicle This information would help determine if your issue matches what I experienced, as oxygen sensor problems can sometimes indicate other underlying issues in the exhaust system.

Thanks for sharing your experience. I got error codes P0135 and P0141 from the diagnostic scan. The check engine light stays on constantly, no unusual smells or sounds from the exhaust. Just had my last service at 41861km. The air-fuel ratio definitely seems off based on my fuel consumption. Interesting that your issue was just a loose connection, hoping mine is similarly straightforward. Did your workshop perform any specific sensor testing before the repair? Let me know if I should gather any additional diagnostic data before booking a workshop appointment.

Thanks for providing those error codes. My situation was nearly identical, I also had the P0135 code in my VW Golf which directly pointed to the oxygen sensor heater circuit. The constant check engine light is a typical indicator of this issue, just as you are experiencing. In my case, the workshop did conduct thorough testing of the heater element before proceeding with repairs. They used specialized diagnostic equipment to measure the resistance values of the sensor heating circuit. This confirmed that while the sensor itself was functioning, the connection issue was preventing proper operation of the heater element. Given your similar error codes and symptoms, especially the increased fuel consumption and air-fuel ratio issues, I strongly suspect you are facing the same problem. The fact that your car components are relatively new with low mileage further suggests this could be a connection issue rather than a completely failed sensor. One thing to note, after my repair, it took about 50km of driving for all car systems to fully reset and the fuel consumption to return to normal. Make sure the workshop clears all stored error codes after the repair. The total diagnostic testing at my workshop took about an hour, and the malfunction indicator light has not returned since the repair.

That was very helpful information about the sensor testing and heater element issues. The error codes definitely match my situation. Going to schedule a workshop visit next week and will make sure they do the proper diagnostic testing you mentioned. Good to know about the 50km reset period, will keep that in mind after the repair. I checked my fuel consumption again today and it is still about 20% higher than normal. At least knowing this is likely related to the oxygen sensor makes me feel better about getting it fixed soon. The constant check engine light is quite annoying, so hopefully the repair will be as straightforward as yours was. Will document all the malfunction indicator patterns and fuel consumption data to share with the workshop. Thanks for explaining your experience in detail, it has helped me understand what to expect during the repair process.