Jaguar S Type Diesel NOx Sensor Causing Exhaust Issues

Had a similar situation with my 2010 Jaguar XF diesel at 95000km. The NOx sensor issue turned out to be quite common, and the symptoms match what you describe, check engine light and exhaust fumes. Initially suspected a full exhaust system problem, but diagnostic tests revealed it was the connection between the NOx sensor and the engine control unit. The wiring harness had deteriorated, causing intermittent signal issues. The catalytic converter and air-fuel ratio readings were normal, confirming the problem was isolated to the NOx sensor circuit. The repair involved replacing both the NOx sensor and the associated wiring harness. This was a significant repair that required specialized diagnostic equipment to properly calibrate the new emission sensor. The job took about 4 hours at the shop. Worth noting that leaving this unaddressed can lead to reduced engine performance and potential damage to other exhaust system components. Would recommend getting it checked soon, as the symptoms you describe are very similar to what can happen when the NOx sensor starts failing. The good news is that if caught early, you can avoid more extensive exhaust system repairs down the line.

Thanks for sharing your experience with the NOx sensor issue. It gives me hope that my problem might be similarly straightforward. Been dealing with similar symptoms on my S Type and your description of the diagnostic process is really helpful. The check engine light has been my main concern. Did you remember roughly how much you paid for the full repair? Also curious if youve had any other pollution control or exhaust system problems since getting it fixed? Knowing the potential cost would help me budget for this and decide whether to use the dealership or look for a specialized shop that knows their way around nitrogen oxide sensors.

Thanks for asking about the follow-up. Since having the NOx sensor issue fixed, my Jaguar XF has been running perfectly with no additional exhaust system problems. The repair was actually simpler than initially expected, turned out to be just a faulty cable connection to the emission sensor that needed fixing. Total cost came to 95€, which was a relief since I was worried about a more expensive repair. The check engine light cleared up immediately after the repair and hasnt returned. The diesel engine is now performing as it should with no exhaust issues. If your symptoms are similar, theres a good chance you might be looking at a similarly straightforward fix. The key is finding a shop that knows how to properly diagnose sensor failure and can accurately pinpoint whether its a connection issue or the sensor itself that needs replacement. Not all sensor problems require a complete replacement, sometimes its just the wiring or connection that needs attention.

Thanks for the advice. Just got back from the mechanic and wanted to share how it went. The diagnostic confirmed it was indeed the NOx sensor causing problems. Total repair cost came to 120€ including parts and labor, more reasonable than I expected. The mechanic showed me where the old sensor had corroded, affecting the air-fuel ratio readings. They found some minor wiring issues too but nothing major with the rest of the exhaust system. The whole job took about 3 hours. Really glad I caught this early before it caused any serious pollution control problems. The check engine light is now off and the engine is running smoothly again with no odd exhaust fumes. Most importantly, the nitrogen oxide readings are back to normal. Definitely feeling relieved it wasnt anything more serious. Good reminder to pay attention to these warning signs early on. Thanks again for helping me avoid a potentially bigger headache with the exhaust system.