S5 TDI Boost Sensor Fault Causing Power Loss

Since you mentioned having an Audi S5 TDI, I can share my experience with a similar issue on my 2021 Audi S4 TDI. Having worked on several car repairs myself, I have some experience with sensor-related problems. The symptoms you describe sound very familiar. My charge sensor and air temperature readings were also erratic, accompanied by that distinctive whistling noise during acceleration. The temperature sensor was giving false readings, which caused the engine management system to reduce power output as a safety measure. Initially, I thought it was the airflow sensor, but when I took it to the workshop, they found a damaged wire connection to the charge air temperature sensor. The complete repair, including diagnostic and labor, cost me 95 Euro. They had to remove parts of the air intake system to access and replace the faulty connection. Before getting it fixed, I tried disconnecting and reconnecting the sensor, but this only provided temporary relief. The proper repair was the only lasting solution. Could you share your current mileage and whether you notice these issues more during cold or warm weather? This information might help identify if your case is similar to what I experienced. Also, have you noticed any changes in fuel consumption since these symptoms started? This detail could help narrow down whether its purely a sensor issue or if there might be related problems in the air intake system.

Thanks for the feedback. After checking the car history, all regular services were done until 102456 KM and all parts were replaced according to maintenance schedule. The temperature fluctuation is most noticeable during cold starts and has gotten worse over the past week. The engine sensor warning appears right after the fluctuation starts. Fuel consumption increased by about 2L/100km since the issue began. The charge sensor readings are highly inconsistent according to the diagnostics data. I noticed the airflow sensor values also spike during acceleration, which matches the timing of the whistling sound. Looking at the service costs, 95 Euro seems reasonable if its just a wiring issue. Will have it checked at the workshop this week.

Thanks for the additional details about your S5. Your symptoms align exactly with what I experienced with my S4, especially the correlation between the whistling noise and irregular airflow sensor readings during acceleration. The cold start temperature fluctuation you mentioned was also present in my case. The air temperature readings would swing wildly on startup, triggering the engine sensor warning. This behavior is typical when the charge air temperature sensor starts failing or has wiring issues. The 2L/100km increase in fuel consumption matches my experience too. This happens because the engine management system receives incorrect temperature data and runs a richer fuel mixture as a safety measure. Based on your mileage and the fact that all maintenance is up to date, a wiring issue is likely the culprit rather than sensor failure. The air sensor wiring can deteriorate over time due to engine bay heat cycles and vibration. The 95 Euro repair cost in my case covered the wiring fix and basic diagnostics. Given the matching symptoms and similar vehicle specs, you should expect comparable costs unless they find additional issues during inspection.

Thanks for sharing your experience. The temperature sensor readings do seem similar to your case. I have continued monitoring the fluctuations and notice the engine sensor warning appears most frequently during morning starts when ambient temperatures are lower. The fuel economy impact of 2L/100km matches what you experienced. The inconsistent charge sensor readings and airflow sensor spikes during acceleration are particularly concerning. These irregular air intake patterns definitely need professional attention. 95 Euro for a wiring repair seems quite reasonable compared to the cost of running with increased fuel consumption. Will get the temperature gauge and sensor connections checked at the workshop. The air intake system inspection should reveal if there are any additional issues causing the whistling sound. I will update the forum once the repair is completed to help others who might face similar temperature sensor problems in the future. Hopefully its just a wiring issue as you suggested and not a more complex problem with the air intake system or engine sensors.