2010 Gen # VSC/TRAC warning comes on after changing front brake pads

Are you sure it isn't the Hill Assist light coming on. When you push the pedal to the floor like that it locks the brakes if you are on a steep incline. A light will appear until you release the brake. As soon as you release the brake pedal you have about 1 second to get to the throttle.

 

Sounds like you might have air but you can check the fluid level if it's too high or too low.
You can try "resetting" the system. Turn off the car, then unplug the negative from the 12V battery and leave unplugged for at least 90 seconds. Plug back in and test it.

As I remember you were supposed to disconnect the 12V. I even read somewhere to keep the car key away from the car while changing the pads.
HOW TO : Replace Front Brake Pads and Discs (Rotors) Prius Gen 2 | PriusChat

 

"should have" unhooked the 12v, sounds like exactly what it "would have" prevented happened, better tow to a Toyota dealer and let them computer it back into operation. "couda"

 

At this point, I would take it to the dealership, let them sort it out. Next time:

Disconnect the 12 volt negative cable first. Then, before reconnecting it, pump the pedal, firm it up.

 

The brake system will go into a default mode, if something is messed up. I know, I've had it happen, for no apparent reason, about 4 times now. Get lotsa lights, and a strange "shift" in brake feel. They still work, but less responsive. When it happens, I just run it down to the dealership, they hook it up to Techstream, fix it. They're still not sure what's happening.

In your case there seems to be a definite cause-and-effect. I doubt you've got air in the system, assuming all you did was push the piston back to accommodate new pad. I would just let them check it out, do tell them what you did, it'll help with diagnosis. They'll likely just hook up their computer, work their magic. And next time do the 12 volt disconnect.

There is also a jumper trick you can do, a paperclip between 2 pins in OBD, but at this juncture, I'd go to the pros.

 

This is just an idea. Did you by any chance greased up the breaking discs or the pads?

 

Assume by "pads were greased" you're meaning lubricant applied at all the points of contact, the usual application. @Piotrus Pan was wondering about grease contamination on the working face of pads and/or the rotor surface.

I guess you're not going to get it checked out by the pros?

 

There's no way under normal circumstances you should be able to press the brake pedal to the floor. You have a definite problem. On my CT I disconnected the battery and kept the key fob well away from the car. After all pads were changed everything was fine when the battery was re connected. I would get yours checked immediately.


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