Nissan 350Z check engine light and fuel consumption

Those are classic knock sensor symptoms. Have you checked the wiring and plug connection to the sensor? A faulty connection there can trigger those issues without the sensor itself being bad. What's the mileage?

Yeah, I checked the plug, seemed okay. Mileage is at 220306 km. What else could cause the light if it's not the connection?

Given the mileage and symptoms, a failing knock sensor is quite likely, especially if the wiring looks good. However, those symptoms can also indicate other engine issues. Considering the potential impact of a faulty knock sensor on engine timing and performance, I suggest having it properly diagnosed at a workshop. They can confirm the sensor's functionality and rule out other potential problems.

I appreciate the input. I dropped it at the shop; it was the knock sensor connection. They cleaned it up, and all is good now. Cost me 95€.