Smart Fortwo Diesel Power Loss Due to Bad Temp Sensor

Had similar symptoms with my Smart Forfour CDI from 2006. The exhaust temperature sensor failure caused engine management issues, increased fuel consumption and significant power drops during acceleration. The exhaust system inspection revealed a small leak near the sensor connection point, which was corrupting the readings. The engine management system was getting incorrect data, causing it to run rich and trigger the check engine light. This turned into a more serious repair than initially expected. The leak was allowing exhaust gases to escape before reaching the sensor, leading to incorrect temperature readings. The repair required replacing both the exhaust temperature sensor and fixing the leaking section of the exhaust system. After the repair, fuel consumption returned to normal and the power loss issue disappeared completely. The check engine light cleared after the new sensor was properly calibrated to the engine management system. Worth noting that leaving this unrepaired can cause additional problems with the DPF system and potentially lead to more expensive repairs. Recommend getting it checked soon, focusing on both the sensor and potential exhaust leaks in that area.

Thanks for sharing that experience. My situation sounds exactly like yours, including the power loss and high fuel usage. Just scheduled a repair for next week. Quick question, do you remember roughly how much you paid for the exhaust temperature sensor replacement and leak fix? Also, has everything worked properly since the repair, or did you notice any other emission control issues?

Just got back from the repair last week actually. The exhaust temperature sensor replacement fixed all those annoying power and fuel consumption issues completely. Since the sensor repair and leak fix, the engine management system works perfectly, no more check engine light or performance problems. Total cost came to 265€ for fixing both the exhaust system leak and replacing the faulty sensor. Money well spent considering how much extra fuel I was burning before the repair. No emission control issues since then. The car runs like new, with normal fuel consumption and proper power delivery. The temperature sensor now gives accurate readings to the engine management system, which makes a huge difference in how the engine performs. If your symptoms match what I experienced, getting both the sensor and checking for exhaust leaks is definitely the right approach. A proper repair should sort out all those issues in one go, just like it did with mine.

Thanks for the input. Just got back from the mechanic and wanted to share my experience. The repair went smoother than expected. The technician found both a faulty temperature sensor and a small crack in the exhaust system near the sensor mounting point. This explained the temperature fluctuation issues that were causing my engine problems. Total bill came to 290€, which included the new sensor, exhaust repair, and labor. Bit more than expected but worth every cent. The car runs perfectly now, no more power loss, fuel consumption is back to normal, and the check engine light has stayed off. Quick shoutout to the mechanic who took time explaining the emission control system and showed me the old damaged parts. Much better experience than my previous repair attempts. Will update if any issues pop up, but so far everything works exactly as it should. Thanks again for helping me diagnose this correctly.