Audi Q5 Hybrid NOx Sensor Issues And Exhaust Leaks

Having worked on my 2016 Audi Q7 Hybrid, I can share my relevant experience with a similar sensor failure issue. The symptoms you describe match what I encountered, check engine light and exhaust system concerns. In my case, after diagnostic testing, the workshop found a faulty connection between the emission sensor and its wiring harness. The air-fuel ratio readings were inconsistent due to this connection issue. The repair involved cleaning the connector terminals and replacing a damaged cable section. Total cost was 95 Euro, which included diagnostic testing and labor. The fix resolved both the sensor readings and the check engine warning. Before suggesting specific next steps, could you share: Current mileage on your Q5, Any recent repairs or maintenance, Whether the check engine light is steady or flashing, The specific fault codes from the scan This information would help determine if your issue matches the wiring problem I experienced or points to a different emission sensor concern. Until then, recommend limiting long-distance drives since sensor failures can affect engine performance and potentially cause increased emissions.

Latest service was at 36700 KM in December, with my current mileage at 37458 KM. Actually the fault codes showed P0420 and P0430, which point to the catalytic converter efficiency. The exhaust leak seems more serious now, with visible smoke and a strong smell, especially during acceleration. My pollution control system might be compromised based on the latest diagnostic readings. The air-fuel ratio values are way off normal parameters according to the scan tool. The diesel engine performs fine otherwise, maintaining good power delivery and normal fuel consumption. Still planning to get it checked this week but wanted to confirm if anyone had similar readings at relatively low mileage like mine.

Thanks for providing those details. Your situation sounds more complex than my initial wiring issue, especially with those specific fault codes and the worsening exhaust leak symptoms. On my Q7, when I later encountered P0420, it indeed signaled a failing catalytic converter, not just a sensor problem. The pollution control system showed similar inconsistent readings. The smoke and strong exhaust smell you describe match what I experienced before getting mine fixed. In my case, the workshop found that the original NOx sensor issue had caused prolonged rich fuel mixture, which damaged the catalytic converter. The complete repair included: New catalytic converter, Replacement of the exhaust system gaskets, Updated NOx sensor, Full emission sensor calibration Total repair cost was 1850 Euro, significantly more than my initial sensor fix. However, it completely resolved both the check engine warnings and exhaust leaks. With your low mileage, this could be covered under extended warranty if you have it. The combination of P0420 and P0430 strongly suggests catalyst efficiency problems rather than just sensor issues. Would recommend getting this checked immediately, as continuing to drive with these symptoms could lead to more extensive exhaust system damage.

The situation seems more serious than I initially thought. Let me share my latest findings since posting this question: Current readings from my diagnostic tool confirm the catalytic converter efficiency codes P0420 and P0430 are persistent. The nitrogen oxide levels are definitely out of spec, which explains the strong exhaust smell getting worse during heavy acceleration. The diesel engine still runs decently but the exhaust leak needs immediate attention. My air-fuel ratio readings keep fluctuating outside normal parameters. The NOx sensor data suggests the pollution control system is not functioning properly. Called two repair shops and got estimates ranging from 1750 Euro to 2100 Euro for a complete fix including: Catalytic converter replacement, New exhaust system seals, NOx sensor replacement, Full system calibration Will schedule the repair this week since driving with compromised emissions could cause more damage. Thanks for confirming this matches your experience with similar symptoms. Just surprised to need such extensive exhaust system work at only 37458 KM, but better to address it now than risk bigger issues.