VW Up Sensor Failures Causing Exhaust Leaks & Warnings

A similar issue occurred with my 2014 VW Polo TSI, also experienced check engine light problems and sensor issues. Having some experience working on cars, I initially tried diagnosing it myself with an OBD scanner. The exhaust system readings were irregular, pointing to potential emission sensor problems. The workshop discovered it was actually just a loose connection, the wiring harness to the sensor had partially detached, causing erratic readings in the pollution control system. The fix was straightforward, they repaired the cable connection and properly secured the plug. Total cost was 95€ including diagnostic work. Since then, the check engine light has stayed off and emissions are normal. To better assist with your situation, could you share: What error codes your system is showing? Are you noticing any performance changes? Have you had any recent work done on the exhaust system? Does the check engine light stay on constantly or flicker? These details would help determine if your issue is similar to what I experienced with the sensor connections.

Thanks for explaining your experience. After reading your response, I checked my error codes again and they point to P0420 and P0135. The service history shows the catalytic converter was never replaced at 13456km. A recent inspection showed the air-fuel ratio is off, which explains the exhaust smell. My symptoms differ slightly, the check engine light stays on constantly and engine performance drops especially during acceleration. No recent exhaust work has been done, but the emission sensor readings are consistently high according to my mechanic's initial scan. Would be helpful to know if a complete catalytic converter replacement was needed in your case or if the wiring fix alone resolved all issues.

The wiring fix alone wasnt enough in my case. After the initial repair, similar issues returned within 2 weeks. The P0420 code reappeared, and my mechanic confirmed the catalytic converter was deteriorating, causing inconsistent nitrogen oxide readings. The full repair ended up requiring: New catalytic converter (850€), Replacement of two oxygen sensors (320€), Updated pollution control module firmware Since completing these repairs 6 months ago, my VW Polo runs perfectly, no check engine lights, normal acceleration, and proper emissions. Your symptoms sound nearly identical to what I experienced, especially the constant warning light and performance issues. Given your car has the original catalytic converter with significant mileage, its likely reaching end of life. The high sensor readings and exhaust smell strongly suggest converter failure rather than just sensor issues. The complete fix isnt cheap, but waiting too long risks further engine damage. The catalytic converter plays a crucial role in the pollution control system, and when it fails, it affects overall engine performance. What did your mechanic say about the condition of your oxygen sensors? In my case, they were also damaged from the failing converter.

Thanks for the detailed case comparison. Your repair path makes a lot of sense given what I'm experiencing. I had the oxygen sensors tested yesterday, both upstream and downstream sensors show degraded performance according to the scan results. The mechanic agrees the catalytic converter is likely the core issue, with the sensors being collateral damage from running too long with a failing converter. Given the similar symptoms and diagnostic results, I will proceed with replacing both the catalytic converter and sensors. The cost is significant but seems necessary to restore proper emission control and engine performance. The consistent check engine light, poor acceleration, and high NOx sensor readings leave little doubt about needing the full repair. Will schedule the work next week and make sure they update the control module firmware as part of the service. Good to hear your car has been running well for 6 months after the complete fix. Hoping for similar results once all components are replaced and properly calibrated.