S90 diesel exhaust temperature issue

Hey. Those symptoms point towards an exhaust issue. Have you noticed any unusual smells or sounds from the exhaust system? Is a leak possible? That could mess with the temperature readings.

I haven't noticed unusual smells, but I can't rule out an exhaust leak. If it's a leak, would that be the primary cause? Wouldn't the sensor just report the actual temperature, leak or no leak?

A leak would cause temperature readings to fluctuate outside the expected range, triggering the sensor and warnings. While the sensor could be faulty, a leak is common. I'd suggest getting it checked at a workshop. They'll be able to diagnose it properly and save you money on unnecessary sensor replacement.

Thank you so much for the advice! You were spot on. Took it to a local workshop, and it turned out to be a small crack in the exhaust. They replaced the cracked exhaust component and the temperature sensor as you recommended and all is well. Total cost was 265€. Really appreciate the help!