Peugeot 407 exhaust leak

Sounds familiar. I had a similar problem with my old Opel Astra: check engine light, sluggish performance. Could be the exhaust temperature sensor, especially if you suspect a leak. Is the exhaust unusually loud?

Loud, you say? Now that you mention it, there is a slight hissing sound coming from underneath the car. Where was the leak in your Astra's exhaust system, and how did that affect the temperature sensor readings?

The leak in my Astra was near the catalytic converter. The garage guys told me that the leak messed up the sensor readings, causing the engine to run poorly. Honestly, I would recommend taking it to a workshop.

After your advice, I had my 407 inspected, and a small leak in the exhaust system was the culprit, damaging the exhaust temperature sensor. Repair cost 265€. I'm glad for your help!