T-Roc NOx Sensor Fault After Failed Exhaust Repair

Had similar problems with my 2015 VW Golf TSI. The nitrogen oxide sensor fault triggered the check engine light, causing inconsistent air-fuel ratio readings. The root cause was a corroded wiring harness connecting to the NOx sensor, not the sensor itself. The previous exhaust system work likely disturbed these connections. Moisture and heat exposure near the exhaust components had degraded the cable insulation over time. The fix required replacing the entire wiring harness segment and installing new weatherproof connectors for the pollution control system. This was crucial since faulty NOx sensor readings can cause improper fuel mixture and potential engine damage if left unfixed. Looking at your symptoms, suggest checking the wiring connections first before replacing expensive components. The connection points often accumulate debris from road conditions which can create false sensor readings. Any qualified VW specialist should be able to properly diagnose whether its a wiring issue versus sensor failure using the right diagnostic tools. This repair is relatively straightforward for an experienced technician but requires careful attention to proper routing of the new harness away from hot exhaust components.

Thanks for sharing your experience. The wiring harness issue matches what I was dealing with. My check engine light started flashing after getting the exhaust worked on. The emission sensor readings were all over the place until we tracked it down to damaged wiring. Before spending money on parts, did you get a final cost breakdown for the repair? Would be helpful to compare prices. Also curious if the problem stayed fixed or if you noticed any other sensor failures popping up since then? Had some odd readings from my air-fuel ratio sensor last week that got me worried it might be related.

Just got the repair done last week actually, total cost was 95€ to fix the cable and plug connection for the NOx sensor. Much cheaper than replacing the entire sensor unit. The mechanic found the connection point was damaged, likely from the previous exhaust work. Since fixing the wiring, all emission sensor readings have stabilized and the check engine light has stayed off. The air-fuel ratio readings you mentioned are often linked to nitrogen oxide sensor failures, but once the wiring was properly sealed and reconnected, those irregular readings cleared up completely. My advice would be to have a technician specifically check the wiring harness connections near the exhaust components. The diagnostic showed the sensor itself was working fine, it was just getting incorrect readings due to the faulty connection. A proper repair should include weatherproofing the connection points to prevent future issues from heat and moisture exposure. Important to mention that intermittent sensor failures often clear up once the wiring is properly fixed. No other sensor issues have appeared since the repair was completed.

After getting advice here, I took my T-Roc to a different mechanic who specializes in VW diagnostics. The wiring harness inspection revealed exactly what was suspected, damaged connections near where the previous exhaust work was done. The repair cost came to 180€ including diagnostic time and new weatherproof connectors. More than the previous post mentioned, but still way cheaper than replacing the NOx sensor. The catalytic converter and rest of the exhaust system checked out fine during inspection. Happy to report the check engine light has stayed off for the past week. All emission readings are now stable and the engine is running smoother. The air-fuel mixture seems properly balanced now that the sensor is getting accurate readings. Lesson learned about finding a qualified technician who understands these intricate exhaust system components. While the initial mechanic missed the wiring issue completely, the new shop identified and fixed the root cause quickly. Definitely worth getting a second opinion when dealing with sensor-related problems.