Peugeot 806 exhaust back pressure sensor issue

The symptoms strongly suggest a faulty exhaust back pressure sensor. Have you noticed any changes in engine performance or fuel consumption? When was the last emissions inspection?

No change in fuel consumption, but a slight decrease in engine performance. Passed emissions six months ago. Could a clogged catalytic converter make the sensor readings worse?

A partially clogged catalytic converter could influence the exhaust back pressure sensor readings. Given the age and mileage, have a technician assess the entire exhaust system. The sensor issue needs immediate attention, so a workshop visit may be in order.

I visited a workshop. The diagnostic confirmed the defective exhaust back pressure sensor. Replaced the sensor for 245€, which fixed the warning light and smoke. Engine performance is back to normal. Thanks for the help.