Toyota Crown Whistling Noise Power Loss

Sounds frustrating. I had a similar issue with my old 2014 Volvo S60. Same loss of power and weird hissing sound. It also turned out to be sensor-related, though mine was the mass airflow sensor. My mechanic said a faulty sensor will sometimes cause the car's computer to pull back the timing and fuel delivery to protect the engine, which is why you're feeling the power loss. Did you check the sensor's wiring and plug? It could just be a loose connection.

Thanks! I suspected a sensor issue. Any tips on what I should be looking for specifically when checking the sensor's wiring and plug? I'm not exactly a mechanic, but I'm willing to get my hands dirty if it's something simple. Could temperature fluctuation be a sign of this?

Well, in my case, the wire to the MAF sensor had corroded where it plugs into the sensor, which caused a bad connection and tripped the error. You'll want to check that the connector clicks firmly into place and that all the wires going into the connector are secure. Also, look closely for any signs of damage to the wiring, like cuts, frays, or corrosion. If you're not confident working on it, I'd advise taking it to a workshop to be on the safe side. The computer can do more damage if the wrong values are used.

It turned out the whistling was a split in a hose connected to the intake, but the charge air temperature sensor error was indeed a defective plug. Replaced the plug, fixed the hose, and she's running like new again! Cost me about 95€.