Trafic exhaust temperature sensor fault

I drive a Trafic as well. Had similar issues, although mine started a bit earlier in its life. Are you noticing any unusual noises coming from under the vehicle, especially when it's cold?

Unusual noises? Hmmm, now that you mention it, I do hear a slight hissing sound sometimes, mostly on cold starts. Could a small leak really throw off the sensor that much?

That hissing could very well be your culprit. A leak upstream of the sensor can definitely mess with the readings. Honestly, with those symptoms, it's best to get it checked by a workshop. Don't keep driving it like that!

Took your advice and brought it in. Turns out, you were spot on – small crack in the exhaust manifold. Replaced the sensor while they were at it. Total damage: 265€. Runs like a champ now! Thanks for pointing me in the right direction; really appreciate it!