C5 Charge Air Temperature Sensor Error

Whistling and hissing usually points to air leaks. But with a temp sensor error code and reduced power, it's likely the ECU is pulling back performance due to faulty sensor readings. Do you have access to live data? Seeing the temperature values reported by the sensor when the engine is running or even just idling would be helpful. Does the temperature fluctuate wildly or remain stuck at an implausible value? Or is it simply out of range?

Thanks for the quick reply. I do have access to live data. Where would I find the sensor you're referring to, and what range of values would you expect to see?

Okay, the charge air temperature sensor is typically located on the intake manifold, downstream of the turbocharger and intercooler. Expected values depend on ambient temperature and engine load, but at idle, you should see something relatively close to ambient. Under load, it'll climb, but it should be a smooth increase, not erratic jumps. Considering your symptoms, specifically the hissing and the error code, and without further diagnostics, I would suggest you might need to get it to a workshop.

Thanks, that confirms my suspicions. I'll take it in. Just wanted to be sure I wasn't missing something obvious. It was indeed a defective connection, as I first thought - 95€ all in.