Peugeot 407 check engine light and reduced power

I've got a 407 as well. Your symptoms sound very familiar. The IAT sensor can definitely cause those issues. Have you checked the wiring to the sensor? Sometimes a loose connection or damaged wire can trigger the same errors as a defective sensor.

I haven't checked the wiring yet. Where is the sensor located and what specific points should I inspect on the wiring?

The IAT sensor is usually on the intake manifold or somewhere in the air intake tract. Check the connector first, make sure it's clean and properly seated. Then, visually inspect the wires for breaks or frays. Honestly, even if the wiring looks okay, if the symptoms are persistent and you've got the error code pointing to it, it's most likely the sensor itself. I ended up just taking mine to a workshop.

I'll inspect the wiring. Given the persistent symptoms and the error code, I'll likely consult a workshop as well. The repair cost 155€