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For short bursts of acceleration, pressing down on the accelerator causes a whining sound that persists even after turning off the engine.
Just what is it?

That "whining" sound is actually unique to your 2025 Toyota C-HR Design, but it could be either completely normal or indicate that you should take your car to the dealer.
1. The (Regular) "Hybrid Whine"
One such self-charging hybrid is the 2025 C-HR. To "put your foot down," the electric motor and petrol engine collaborate.


The Noise: When a hybrid is under severe acceleration or regenerative braking, it makes a high-pitched electrical whine, like a spaceship or a tram.
Despite turning off the engine, the car's electrical systems do not "die." This is why the problem persists. There is usually some level of activity from the hybrid battery cooling fan and the EVAP system, which monitors for fuel vapour leaks.
Findings: The heat management system is probably just doing its job if the sound is a constant, high-pitched "electric whirr" that goes away after a couple of minutes.

Secondly, the continuously variable gearbox (watch this)
A CVT, or continuously variable gearbox, is utilised by the C-HR. In spite of the improvements made to the 2025 models, the C-HR has a reputation for "CVT whine."

The Symptom: A problem with the bearings could be the cause if the whine sounds more like a mechanical siren or a "whirring" that becomes louder as you increase the speed, instead of only during the "spurt" itself.
The Test: If the whine remains audible even when coasting or if it resembles metal-on-metal, then the noise is coming from the gearbox and not the hybrid system.

3. Servos and Electronic Parking Brakes
Electric features abound in the "Design" package. The electronic parking brake engages and several actuators (tiny electric motors) return to their "home" places when you turn off the automobile. From below the vehicle, you might hear what sounds like a succession of mechanical whirs or zips.
The following steps:

Look for the "Ready" light; if it's on and the engine is off, and the noise persists, it's probably an electric cooling fan.
Start timing the noise once you switch off the engine. If it continues for more than 5–10 minutes, it could be due to a sensor malfunction or a stuck relay.
Your purchase is fully warranted by Toyota's factory warranty due to the fact that it is a 2025 model.

Could you tell me if the noise was coming from the car's engine or motor or its fuel tank or battery?

Out of Gemini AI

Possible sources of the noise include the pedestrian noise generator (which can produce noises up to 15 mph when the vehicle is in EV mode) or the cooling fans for the climate control, heat pump, hybrid inverter cooling system, or HSD cooling system (the latter two of these systems use the same cooling fan, so they're essentially interchangeable).

It took me a while to figure out that my 2008 Prius was making a whining noise whenever I cranked up the accelerator. I hadn't realised that the JBL Stereo system had an AUX input until I noticed that I had connected an audio wire, but my iPhone wasn't in the car.
The sound abruptly ceased after I removed it from the AUX selection.

I remember that while my 18-year-old Prius's air conditioner was running, it produced a clear high-pitched noise. Now I'm wondering if it was the compressor fan, which also made a clear high-pitched General Electric Turbofan noise.

In order to positively identify the sounds, I recommend rolling down your front windows and conducting further investigation.

Identifying the source of the noise is overwhelmingly challenging. However, it lacks the characteristic fan sound. I will give coasting a go the next time it happens to see if it still runs.