VW Tiguan's Exhaust Sensor Drains Power and Fuel

Had almost the exact same problem with my 2015 VW Golf TDI. The symptoms you describe match perfectly, reduced power, higher fuel consumption, and that annoying engine light. Got it checked at my regular workshop where they diagnosed a leak in the exhaust system near the temperature sensor. The exhaust component was damaged, causing incorrect readings from the sensor. The entire repair, including sensor replacement and fixing the leak, cost me 265€. After the fix, the car ran perfectly again, normal power restored and fuel consumption back to standard. These emission control system issues are quite common in VAG diesel engines from that era. The temperature sensor plays a crucial role in the exhaust system monitoring, and when it gets faulty readings due to leaks, the engine management goes into safe mode. Could you share: Current mileage? Any unusual sounds from the exhaust area? Were there any warning messages before the engine light came on? Have you noticed any black smoke from the exhaust? This information would help confirm if your issue matches what I experienced. These car exhaust problems can be tricky to diagnose without proper inspection, but the symptoms you describe are very familiar.

Last service was done 2 months ago at 39684km. Regarding sounds from the exhaust, nothing unusual to report. No warning messages appeared before the check engine light, and definitely no black smoke visible. The engine management system just suddenly went into reduced power mode during normal highway driving. The heat sensor readings must be looked at more closely, since the engine runs smoothly otherwise. Thanks for sharing your repair experience, the cost seems reasonable if it solves the issue completely. The emission control system and exhaust sensors are crucial components, so getting an accurate diagnosis is important. Will have this checked professionally to confirm if the fault matches your case with the temperature sensor. Considering the relatively low mileage, other exhaust components should still be in good condition.

The smooth running engine despite the power reduction does point strongly toward sensor-related issues rather than mechanical problems. When my Golf had similar symptoms, the engine also ran fine otherwise, just with reduced power output. After my sensor replacement experience, I learned these temperature sensor failures often occur without warning. The emission control system reacts immediately when receiving incorrect readings, triggering the power reduction mode for engine protection. Given your low mileage and recent service, I would focus specifically on the exhaust temperature sensor area. My mechanic explained these sensors can fail prematurely regardless of mileage, especially if exposed to extreme temperature cycles. The fact that it happened during highway driving matches my experience, the sensor readings become erratic under sustained load. Since your repair will likely be similar to mine, expect the workshop to: Perform a full diagnostic scan, Check exhaust components around the sensor for leaks, Test the sensor readings at different engine temperatures, Replace the faulty sensor if confirmed The relatively quick onset without prior warning signs matches the typical sensor failure pattern. Once replaced, you should notice immediate improvement in both power and fuel efficiency.

Thanks for sharing those details about your repair experience. The highway driving failure mode matches my situation perfectly. I will focus on getting the exhaust temperature sensor and surrounding components checked first, since all signs point to a sensor issue rather than a larger exhaust system problem. The diagnostic steps you outlined make sense, especially checking for any leaks around the sensor that could cause incorrect readings. The engine management system seems very sensitive to these temperature sensor failures, but I guess that is better than risking engine damage. Will book it in this week for testing, hoping for a straightforward sensor replacement like in your case. The smooth running engine despite reduced power does suggest the core engine is healthy. Looking forward to getting back normal performance and fuel economy once the emission control system is working properly again. My only concern is if there could be any connection to the recent service, but the timing might just be coincidental since these temperature sensors can apparently fail at any time. Will update the forum once I get the final diagnosis and repair done.