XT5 Exhaust Leak Symptoms Point to Catalytic Issues

As someone with some experience working on similar issues, I dealt with almost identical symptoms on my 2017 XT5. The engine light came on and I noticed similar exhaust problems along with rough running. After taking it to a workshop, they performed a diagnostic scan which revealed a faulty Lambda sensor. The sensor readings were causing incorrect fuel mixture, leading to poor performance and that strong exhaust smell. They also found the catalytic converter was getting excessive fuel due to this issue. The repair cost was 375€ which included parts and labor. They also inspected the entire exhaust pipe system to ensure there were no additional leaks or damage to other components like NOx sensors. The fix completely resolved the rough running and eliminated the exhaust smell. The engine light cleared up immediately after the repair. To better assist with your specific case, could you share: Current mileage on your XT5, When did these symptoms first appear, Have you had any previous exhaust system repairs, Are there any other warning lights on the dashboard, Does the problem get worse when the engine is cold or warm This information would help determine if your issue is similar to what I experienced or potentially something different in the exhaust system.

After checking fault codes and speaking with my service advisor, the issue was traced to a malfunctioning EGR valve and failing oxygen sensor. The diagnostic showed both components were causing improper exhaust gas recirculation and fuel mixture problems. Last service was at 165000 KM, and these problems started shortly after. The rough running and exhaust smell got noticeably worse over about 2 weeks. My mechanic found carbon buildup was restricting the EGR valve operation, while the oxygen sensor was giving incorrect readings. Total repair cost came to 450€ including parts, labor, and a complete exhaust system inspection. The fix resolved all symptoms and the check engine light cleared immediately. Sharing this in case others face similar exhaust system problems. Would recommend having your NOx sensors checked too, as they can cause similar symptoms when failing. Getting ahead of potential issues can prevent more expensive repairs later.

Thanks for sharing your repair experience. Your case is very similar to what I faced with my XT5. After my Lambda sensor repair, I also had to replace the EGR valve about 6 months later when the check engine light returned. The carbon buildup you mentioned is a common issue that can affect the exhaust system performance. The oxygen sensor replacement definitely helped with the fuel mixture, but I learned that regular cleaning of the EGR system helps prevent these issues. Since completing both repairs, my exhaust system has been running smoothly with no catalytic converter problems or exhaust leaks. Good point about the NOx sensors, after my experience, I now have the entire exhaust system checked during routine maintenance. The DEF fluid levels and quality also play a big role in preventing these types of problems. Worth mentioning that following these repairs, fuel economy improved significantly and the engine runs much smoother, especially during cold starts. Preventive maintenance definitely saved me from more costly repairs down the line.

Thanks for all the helpful replies. The repairs to my EGR valve and oxygen sensor have kept my car running great for the past few months. No more exhaust smell or rough running issues. The catalytic converter is also functioning normally according to recent diagnostic tests. For others reading this thread, if you notice similar symptoms, don't wait to get them checked out. What starts as a simple exhaust pipe leak or sensor malfunction can lead to more expensive damage if ignored. The complete diagnostic my shop did revealed the issues early enough to prevent catalytic converter failure. Will definitely keep monitoring my exhaust system during regular maintenance. Having them check the NOx sensors and EGR valve operation has become part of my standard service routine. The 450€ repair cost was worth it to prevent bigger problems. Good advice about DEF fluid maintenance too, I've added that to my routine checks. Always better to catch these exhaust system issues early rather than wait for major malfunctions.