VW Nivus NOx Sensor Leak: Fix Guide & Cost Analysis

Had a similar issue with my VW T-Cross 2021 (some experience with car maintenance). The NOx sensor failure symptoms were almost identical, check engine light and exhaust system problems. The workshop found a damaged cable connection to the NOx sensor. They performed a full diagnostic scan which confirmed the sensor was functioning, but the wiring was the culprit. Total repair cost was 95€ including labor and parts to fix the defective plug connection. My suggestion would be to have a professional diagnose it properly. While NOx sensor issues are common in these engines, the actual root cause can vary. The exhaust leak you mentioned could be related or a separate issue entirely. Could you share: Current mileage on your Nivus, Any other warning lights besides check engine, Specific error codes from the diagnostic scan, Any performance issues (reduced power, rough idle) This information would help determine if your issue matches what I experienced or if it might be something different in the exhaust system.

Latest service was just 2 weeks ago. Current mileage is 35374km. The exhaust leak got worse since posting, with more noise coming from under the car. The diagnostic also showed code P0420, suggesting catalytic converter efficiency issues alongside the NOx sensor readings. Other symptoms after the initial post: Black smoke occasionally visible, Rough idle, especially when cold, Fuel consumption increased by about 15%, No other warning lights The pollution control system seems to be the main concern based on these symptoms. I am planning to take it to the workshop tomorrow for a proper inspection of the entire exhaust system since this might be more than just a sensor issue.

Thanks for the detailed update. These symptoms definitely paint a clearer picture, and they differ from what I experienced with my T-Cross. The P0420 code combined with black smoke and increased fuel consumption suggests this goes beyond the NOx sensor issue I had. Your air-fuel ratio is likely off, and the catalytic converter might be compromised. When my T-Cross had the wiring issue, it never showed black smoke or significant fuel consumption changes. The rough idle and exhaust leak could indicate a crack in the exhaust system, possibly near the catalytic converter connection points. The increased noise you mentioned is particularly concerning, as it could mean the exhaust leak has worsened. Based on my repair experience, get them to check: The entire exhaust system for cracks or loose connections, Catalytic converter condition, All emission sensors including O2 and NOx, Exhaust manifold gaskets My initial repair was simple at 95€, but if your catalytic converter needs replacement, expect costs between 800-1200€ including labor. Get a full inspection before authorizing repairs, as replacing just the NOx sensor might not solve your underlying issues.

I appreciate all the feedback on my Nivus issue. After getting these detailed responses and seeing how my symptoms differ from the T-Cross case, I am definitely more concerned about the catalytic converter and overall exhaust system integrity than just the NOx sensor. The black smoke and increased fuel consumption were not present when I first posted, and now that I understand these are signs of potential catalytic converter issues, I am glad I scheduled the workshop visit for tomorrow. The diesel engine problems seem more extensive than initially thought. I will request a complete inspection of the emission sensor system and exhaust components. The estimated cost range of 800-1200€ for a catalytic converter replacement is higher than I expected, but it makes sense given the complexity of the repair. Will update once the workshop completes their diagnostic process and provides a detailed assessment of the exhaust system damage. Thanks for helping me understand that this requires more than just a simple sensor replacement. The input helped me prepare for a potentially bigger repair job than initially anticipated.