VW Arteon NOx Sensor Issues Cause Exhaust Problems

I had a similar issue with my 2020 VW Passat last year and can share my experience, as I have some experience working on VW vehicles. The check engine light and exhaust-related symptoms matched what you are describing. After running my own diagnostic scan, the NOx sensor showed similar error codes. Initially thought it was the emission sensor itself, but it turned out the cable connection to the nitrogen oxide sensor had deteriorated. The fix was straightforward once properly diagnosed. The workshop identified a faulty connection between the NOx sensor and the main wiring harness. Total repair cost was 95€, mostly labor for testing and replacing the damaged wiring connection. This resolved both the check engine light and the exhaust system issues. Before suggesting anything specific for your case, could you share: Current mileage on your Arteon, Exact error codes from your diagnostic scan, Whether the check engine light is solid or flashing, Any changes in fuel consumption, If the issue started suddenly or developed gradually This information would help determine if your issue matches what I experienced with my Passat or if you might be dealing with a different problem in the exhaust system.

Just had the 95000km service done last month, so I am confident we can rule out maintenance issues. The error codes from my scan tool are P0420 and P0130, suggesting catalyst system efficiency below threshold. After your feedback, I checked the NOx sensor connections and found significant corrosion on the wiring harness near the exhaust system. The check engine light has been consistently on, not flashing, and fuel consumption increased by about 12% over the last 3 weeks. The catalytic converter appears intact based on visual inspection, so your wiring harness theory makes a lot of sense. This could explain both the exhaust leak sound and the pollution control system warnings. Will have the workshop check the sensor wiring first before considering more extensive repairs. Thanks for helping narrow down the potential causes. Hoping it is just the wiring like in your case rather than a full sensor or catalytic converter replacement.

Thanks for providing those details. Based on the error codes and symptoms, your situation does sound nearly identical to what I experienced with my Passat. The P0420 code initially made my mechanic suspect a catalytic converter issue, but the corrosion you found on the wiring harness matches my case exactly. The 12% increase in fuel consumption also aligns with my experience. When the nitrogen oxide sensor connection is compromised, the air-fuel ratio control becomes less precise, leading to higher fuel usage. In my case, fuel efficiency returned to normal immediately after fixing the wiring. Had my workshop do a complete emission sensor diagnostic before proceeding with repairs. They confirmed the catalytic converter was functioning properly and the issue was isolated to the wiring harness near the NOx sensor. The corrosion was causing intermittent signal interruptions, throwing off the entire emission control system. One recommendation: have them check all nearby wiring while they are at it. In my repair, they found minor corrosion starting on other sensor connections and treated those preventively. This avoided potential future issues with the air-fuel ratio sensors in the same area. The repair should be similarly straightforward and cost-effective if your issue matches mine. Much better than replacing the entire catalytic converter or sensor unit unnecessarily.

The symptoms and diagnostic findings look very similar to what both of us experienced. The corrosion on my wiring harness near the exhaust system matches exactly what you described with your Passat repair. Having similar error codes P0420 and P0130 and the matching 12% fuel consumption increase, I am more confident now that we are dealing with wiring issues rather than a failing catalytic converter. The consistenly lit check engine light rather than a flashing one also supports this theory. I will definitely ask the workshop to perform that complete emission sensor diagnostic you suggested before any repairs. Makes sense to verify the catalytic converter function and isolate the issue to the nitrogen oxide sensor wiring. Good tip about having them inspect nearby connections while they are in there, could save me from future air-fuel ratio sensor problems. Your repair experience gives me hope this will be a straightforward fix without needing expensive component replacements. Will schedule the diagnostic inspection this week and have them focus on the wiring harness first. The repair cost around 95€ seems much more reasonable than replacing major parts. Thanks for the detailed comparison. Your feedback helped me avoid potentially unnecessary repairs and narrow down the likely cause. Will post an update once the workshop completes their inspection and repairs.