Seat Arosa Diesel Engine Issue

That sounds awfully familiar! I own an Arosa too, with a diesel, though I can't remember the exact year off the top of my head. I had nearly identical symptoms last year: check engine light, sluggish performance, and my fuel consumption was noticeably worse. Turns out it was also related to the exhaust system, probably related to the heat sensor. Did you notice any unusual sounds coming from under the car, particularly when accelerating? It could point to an exhaust leak somewhere.

Interesting. I haven't really paid attention to the sound, but now that you mention it, there might be a slight hissing noise. I will have to pay more attention to it. How did you manage to resolve the issues that you had and what did it involve? I am trying to understand whether sensor replacement is the only option.

The hissing sound is a pretty good indicator of a leak, I'd say. I spent ages trying to sort it myself, checking all the visible exhaust joints, but I couldn't find anything obvious. In the end, I bit the bullet and took it to a repair shop. They ran diagnostics and quickly pinpointed a fault with the exhaust temperature sensor; they also found the leak in the exhaust system contributing to the temperature fluctuation. I know that not all exhaust issues require sensor replacement, but in my case the sensor wasn't working correctly. My advice? Get it properly diagnosed. It might save you money in the long run. Good luck!

I appreciate you sharing your experience. It certainly helped. I took it to a workshop, and they confirmed a faulty exhaust temperature sensor. The sensor replacement was indeed needed, and it seems there was a small leak in the exhaust system contributing to temperature fluctuation and the sensor failing. They located and fixed the exhaust leak and also carried out the sensor replacement. The total was 265€, but at least my Seat Arosa is running smoothly again.