this noise almost sounds like when you are going downhill and you put the gear to B, and it charges the battery. anyone know what this could be? again it only happens at high speed around 55mph and you take your foot of the gas when exiting a ramp or curving through a ramp.
I noticed it happens when battery us 100% charged. So just push the gas pedal and o increaae speed .this will drain the battery and let the car out of B mode
thats your engine at a higher rpm load to assist with braking. Like when manual cars downshift without using the brakes. Its doing what its suppose to do. Edit .... "^the noise sound like" ... sorry for the mistake OP.
I bought the car new back in 2012. it have 147k now. i never change the 12v battery or change any spark plug. about a week ago up here in MN it’s cold averaging 10 degrees. when i start the car in the morning going to work the engine seems to struggle and hesitate to stay on(I’m thinking about putting in new spark plug and 12v battery) But still seems odd to me about that engine noise at high speed just because i took my foot of the gas pedal. This never happen before til after the engine thingy.
But the thing is I’m not in gear “B” or stepping on the brakes. Just like when you lift up your foot to decrease the speed. It shouldn’t sound like when in “B” mode going downhill using the engine to help brake/slow down the car.
@Pao Yang I would take it in to have it checked out. It could be a transmission whine where an internal bearing may be failing since its happening at higher speeds without load, or something with the engine itself. Hopefully it’s something minor and a quick fix.
Just got done installing new NGK iridium spark plugs. Let’s see how it goes for the next couple of days
Whats the battery level when it happens? Is it full? At what speed does it happen? Can you see a charge to the HV battery or theres no charge? It happens to me a lot when battery is full. So i noticed that increasing speed a bit will stop it and since HV battery drains a little than this humming noise is gone.
Battery level almost full when this happens. This happens at speed around 50mph(doesn’t happen all the time,but this never happen before in my 7 year ownership ) I could see a charge going to the battery when this happens.
still humming from engine after new NGK spark plug install. But again it’s 1 degrees up here in MN today. windchill is negative 10. I’ve noticed the humming happens when it’s charging the battery
@Pao Yang ... i'm not sure if it helps, but my prius is currently at the dealer for another issue, however, they stated that there are some updates to the vehicle. One of which is rough engine sound at startup. Diagnosis for irregular sounds is a hit/miss with forum communities unless its an occurring prevalence.
50 mph is not so high. It seems like car goes to engine brake mode. Basically same like B mode. I know this is a strange advice but Try to shift into N for a short period. Noise will disapear. Or just drive faster. Thats what i do when my battery is fully charged and im on a steep downhill. Increasing speed drains the battery and stops " engine brake"
