Prius makes sounds when I brake and after I step on the gas.

i know the prius goes nuts when the start battery is weak . i have repplaced the start battery tewice on my Prius.both times the car wad raelly weird. one the new battery is properly istalled the car returns to normal.

VSC ABS and ! lights plus red (!) - Toyota Prius Forum ...

www.priusonline.com/...toyota-prius.../19804-vsc-abs-lights-plus-red.ht...

Jun 3, 2008 - 8 posts - ‎3 authors
If the accumulator fails, you will get a red brake warning light and the pump will now run continuosly until it burns out. ... hydraulic pressure to the brake system and "no"red warning lights. .... Fog Lights, PassGas, Toyota Prius General Discussion, 4, 10-13-2005 09:12 AM ... 11-13-2015 10:01 PM by Tim Lee.

Alarm with Brake Light, ABS, VSC and amber warning lights ' PriusChat

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Jul 26, 2005 - Later that same day - I started getting an alarm - as soon... ... Gen 2 (2004-2009) Toyota Prius Forums > Gen 2 Prius Care, ... Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by NorthStar, Jul 26, 2005. ... I am getting the red BRAKE LIGHT, the amber waming symbol, ABS, and ... VSC, ABS, (!) and emergency brake light on
Feb 5, 2010
Brake, Brake warning, ABS, VSC appear
Oct 5, 2008
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• Knowing the warning signs of impending trouble can go a long way toward keeping your car from a highway breakdown.
  
  You need to develop an awareness of how your car should sound. For instance, when you turn the key to start, the gear like sound of the starter motor engaging should be smooth and sound like an electric motor working hard to crank the engine. If you notice a different sound - more like a grinding - chances are you have a starter motor problem about to happen. Let's say you're driving along and you feel the steering wheel vibrating at certain speeds. The onset of this subtle vibration could tip you off to a tire that needs to be balanced, worn steering linkage or a bulge in a tire that may be about to blow out. In any case, the vibration needs attention. Normally you shouldn't notice the sound of the exhaust system. A sudden change in your car's sound, therefore, isn't something to ignore.
  
  Suppose you're used to a pleasant hum, then, perhaps after a bump or when starting up the car one morning, there's a loud roaring that sound like a hot rod without a muffler. The harder you press the gas pedal. The louder the noise becomes. A noisy exhaust means the exhaust gases are blowing out under the car rather than at the rear of the car - a dangerous condition. Brakes play their own warning tune. On many cars, a scratching noise coming from the wheels that stops when you stop pressing on the brake pedal is caused by a low-brake warning device. Its purpose is to warn you that you need front brake pads. A loud grinding noise when you step on the brake pedal is an alarm that your brakes need immediate attention. The grinding noise occurs when the brake pads are totally worn away and the metal of the brake pad backing plate rubs directly on the brake rotor.
  
  Ignoring grinding brakes can be a costly - or even deadly - error. Shock absorbers help keep the car steady and balanced while the wheels roll over bumps and ruts. Their modern counterpart, the MacPherson strut, does essentially the same thing. You might not notice worn shocks or struts when you're simply riding around town. The safety effect of these devices comes into play at higher speeds. When you hit a bump, the tire wants to bounce like a basketball. Worn shocks or struts allow the ties to bounce out of control making steering difficult and braking less effective.
  
  What you may notice is the car rocking more every time you stop, assuming an almost boat like quality. Old, broken or worn out shocks and struts should be replaced to ensure safe steering and braking at higher speeds. Engine noises are easiest to hear when the car is not moving. Transmission sounds or brake noises usually occur when the car is moving. Pay attention to any new sound and keep notes - how it sounds, when it makes the sound and what difference, if any, occurs in driving when the noise is present - to help you describe it to your service dealer.

You just answered your own question. Have your brakes checked.

sounds like the battery plugs on the passenger side were disconnected and not connected. I don't think the brake sensor connectors have to be messed with in the wheel wells to change the struts but if you did you need to reconnect them checking for dirt in the connectors. It has been a long time so I hope you found the problem by now.

You'll have to determine which wheel the sound is coming from and check it again. It could be something hitting the rotor or drum other than the shoes and pads. Like a brake spring or guide.
You can raise each front wheel one at a time and have someone step on the brakes while you listen too. This may turn on the ABS light however.

reset the ERCM using a scan tool
while the brake pads looked fine , the rotors should be removed as that gives the same impression as the abs in operation
there could be a cracked rotor causing the noise
take it to an accredited brake specialist shop

check wheel bearing, sounds like that might be it. I've had cars and trucks that had made that sound and it was the wheel bearing.

i would check the brakes and make sure that they dont need to be replaced check front and back

If this noise happens on wet or humid days this is natural