Mercedes SL Charge Air Temperature Sensor Issue

Whoa, that sounds unpleasant! A whistling noise that turns into a hiss usually means air leaks, especially with a charge air temperature sensor error. The sensor is telling your car's computer the air coming in is either too hot or not right, hence the reduced power. The hissing is likely the air escaping. Check all the hoses and connections related to your air intake system first. Sometimes, it's just a loose clamp or a cracked hose. Is the sensor easily accessible? Have you visually inspected the wiring and connector for any damage or corrosion?

The sensor is accessible. When checking the hoses and connections, are there any specific areas that are more prone to failure or require particular attention?

Since it's accessible, that's good. Pay close attention to any spots where the hoses bend or rub against other components. Those are high-stress areas. Also, feel around the connections themselves – sometimes a hose can feel okay, but it's actually cracked on the underside. Since you've got the air sensor error, it might be best to take it to a workshop. A professional can do a smoke test to find leaks you might miss and properly diagnose the sensor itself. The error memory information will help them too.

I took the car to a workshop. It was a faulty connection at the charge air temperature sensor; the cable connection was defective. The repair was 95€, including parts and labor. The car is now running great.