Ford GT Lambda Sensor Issue

The symptoms you describe, particularly the rough running, strong exhaust smell, and the check engine light, do suggest a potential issue with the lambda sensor, especially given the relatively low mileage. Have you checked for any error codes using an OBD-II scanner? This would help narrow down the possibilities. Has the DEF fluid level been checked recently? A malfunctioning DEF system could possibly trigger similar symptoms. Please provide the exact error code, if available.

I did scan it and it's throwing a code pointing to the lambda sensor. The DEF fluid is topped up, so that's not the issue. Is it likely that a faulty lambda sensor would cause all these symptoms at once? The rough running is what worries me the most, I didn't think a sensor could cause that!

Given the error code confirming the lambda sensor and the elimination of DEF issues, it is highly probable that a defective lambda sensor is the root cause of all observed symptoms. A malfunctioning sensor can indeed lead to an incorrect air-fuel mixture, causing rough engine running and increased emissions, hence the smell. While further diagnostics are possible, I would suggest consulting a qualified workshop to confirm the diagnosis and proceed with replacing the sensor. This will likely resolve the problem.

Took it to my trusted mechanic and you were spot on! It was the lambda sensor, causing havoc with everything. Replaced it for 375€ and the GT is purring like a kitten again. Thanks for the help!