wining noise

Need more specifics: What speeds, is the ICE running, or just electric power? How does the car drive? MPG?

The inverter does make some high pitched noise when larger amounts of current flow through it, but it is normally hard to hear.

To be more correct, in the Prius there is no gas pedal per se, since sometimes pressing it won't turn on the ICE. Accelerator pedal is better.

 

Confused now. Happens when stepping on pedal? Or letting off pedal? The two posts differ.

 

OK. Does the pitch of the noise vary with speed? I.e higher frequency with higher speed?

 

The engine is making the noise for sure. Put the car in inspection mode and the engine will run without you being in the car. Get a flashlight and open the hood and see where the noise is coming from. Items of interest are the engine water pump and the belt area. If whining in the front of the motor shut the engine off and look for green specks in that area indicating coolant seepage from the water pump weep hole usually indicating a bad pump. Check engine oil too.

 

I'm not convinced yet. If the car is warmed up, and the going less than 42 mph, then letting off of the accelerator pedal will cause the engine to turn off, zero rpms, and regenerative braking will occur. If going over 42 mph, the engine will freewheel at some speed, and also regen braking occurs. Since the OP says the noise happens when letting off the pedal at any speed, I would tend to think this has something to do with regen braking. That's why I am curious if the pitch of the noise changes with speed.

Also, the OP could say what the mileage of the car is. Did the noise just appear one day, or come on gradually?

 

Well, I've never hear wine make a noise before (unless you pour it) so the OP must have meant "whining" noise