Viano exhaust sensor problems

A check engine light, reduced power, and increased fuel consumption suggest an engine performance problem. You mentioned an exhaust temperature sensor. Is there evidence of temperature fluctuation? Have you inspected the exhaust system for leaks, as a leak can impact sensor readings?

Temperature fluctuation... I haven't monitored that. An exhaust leak, though – if there was a leak before the sensor, would that mess with the readings enough to trigger these problems?

A leak upstream of the exhaust sensor can introduce ambient air, altering the exhaust gas composition and affecting temperature readings. Given the potential complexity, and to avoid misdiagnosis, a thorough examination by a qualified technician is advisable. They can perform smoke or pressure tests to pinpoint leaks and confirm sensor functionality.

Thanks for the insight. I took it to a workshop, and you were spot on – a small crack in the exhaust manifold was causing the sensor to read incorrectly. Sensor replacement and exhaust component repair came out to 265€. It runs like new again!