Seat Altea Diesel Engine Issues

A check engine light along with reduced power and increased fuel consumption on your Seat Altea usually points to issues in the exhaust system affecting emission control. The exhaust temperature sensor could be faulty as you mentioned. However, diagnosing these issues can be tricky. Have you noticed any unusual noises, like hissing, from the car exhaust when it's running?

No, I haven't heard any hissing. Just the usual diesel engine noise. Is there anything else I should be looking for that could indicate a faulty exhaust temperature sensor? Maybe a visual inspection?

Given the symptoms, especially the increased fuel consumption, it's highly probable that the exhaust temperature sensor is indeed the culprit. Think of it like a domino effect; a small problem with the car exhaust can lead to bigger issues, affecting engine performance and fuel efficiency. I'd recommend getting a mechanic to check the system and carry out a sensor replacement.

Thanks for the advice. The check engine light is now off and the car is running smoothly again. Turns out there was a small leak in the exhaust system near the exhaust component. The sensor replacement plus fixing the leak cost me 265€. Hopefully, this fixes the problem for good.