Audi TT Power Loss Points to Faulty Exhaust Sensor

Had the same issue on my Audi S3 (2018) last summer. The symptoms match exactly, power loss, increased fuel consumption, and check engine light. The exhaust temperature sensor was indeed faulty, but this led to discovering a small leak where the exhaust manifold connects to the downpipe. The heat sensor malfunction triggered the engine to run in safety mode, explaining the power loss. Temperature sensors are critical components of the emission control system, and when they fail, the engine management system reduces performance to prevent damage. A proper diagnostic revealed both the sensor replacement need and the exhaust leak. While the sensor itself is not a major repair, the leak required more extensive work including replacing gaskets and tightening several exhaust components. Before visiting a shop, you can check for exhaust leaks by listening for unusual hissing sounds when the engine is running. A failing temperature sensor often shows specific error codes which can be read with a basic OBD scanner. This turned out to be a serious issue that needed immediate attention, as continuing to drive with these symptoms risks damaging other engine components and further increasing fuel consumption.

Thanks for sharing your S3 experience. The symptoms definitely sound familiar. The temperature fluctuation and engine management issues I experienced were resolved exactly as you described. Quick question, do you remember the total repair cost for both the sensor replacement and fixing the exhaust component leak? Also, has everything been running smoothly since the repair? Just want to make sure no related issues popped up later, as I am trying to budget for the worst case scenario with my TT.

After getting the repairs done, my S3 has been running perfectly with no temperature fluctuation issues. The total bill came to 265 Euro for fixing both the faulty exhaust temperature sensor and the leak in the exhaust system. This included labor and all needed parts. The temperature sensor replacement made an immediate difference in engine performance, and fixing the exhaust leak resolved the remaining issues. The engine management system returned to normal operation right away, and fuel consumption went back to standard levels. Its been several months now, and no related problems have emerged. The exhaust system is working as designed, with steady readings from the new heat sensor. Getting both issues fixed together was definitely the right call, as they were interconnected and could have caused more expensive damage if left unaddressed. For your TT, this repair cost should be fairly similar since the exhaust components and labor requirements are comparable between our models.

Thanks for the input. I finally got my TT fixed and wanted to share my experience. After reading about similar cases, I took it to a certified shop specializing in emission control systems. The diagnosis confirmed both a faulty exhaust temperature sensor and a small leak in the exhaust system. The total repair came to 290 Euro, slightly more than expected but worth every cent. The heat sensor replacement was straightforward, while fixing the exhaust component leak took a bit more time. The difference in performance was immediate. The check engine light cleared, power returned to normal, and fuel consumption dropped back to regular levels. The temperature fluctuation issues completely disappeared. Its been three weeks now and everything runs perfectly. The shop also did a full exhaust system inspection to prevent future problems. For anyone facing similar symptoms, I recommend getting it checked sooner rather than later to avoid potential damage to other components.