Estima Charge Air Temperature Sensor Error

Sounds like a pain. Is the hissing constant, or only under load? Have you checked the sensor's wiring for any obvious frays or loose connections? Start with the basics before assuming the sensor itself has gone bad.

The hissing is worse under load. I looked at the wiring, but didn't see anything obvious. I don't have the tools or know-how for a deep dive. Could it be something other than the sensor or wiring?

Anything's possible, but those symptoms really point to the sensor or wiring. You could chase vacuum leaks, but honestly, save yourself the headache and get it checked by a professional. Probably a quick fix if it’s just the wiring.

Appreciate the advice. Took the Estima to a local workshop, and the cable connection to the charge air temperature sensor was indeed defective. Repair cost 95€, and it's fixed now.