Brake System Issues (ABS, BRAKE, VSC)

It would be sort of irregular, but if you're game to try it, maybe there'd be something to learn from it.

Your original situation did sound a little different from the more common one. The common one is an internal leak bleeding pressure off, so the pump has to run often to replenish it.

From your original description, maybe it did sound like a less common situation with a tired pump motor. Interesting.

 

I don't have any inside knowledge there, sorry. There are some other threads/posts on PriusChat about that. Also, some bulletins went out with part numbers with an 04003- prefix. Not sure what that's about; maybe it was the number for a 'kit' that a dealer would order for doing a replacement.

 

I had all those lights on my 2005 Prius. I tried replacing the skid control ECU unit first. Got it off Ebay. It made sense because it was cheaper. It did not fix the problem. I had less errors but same hard brake pedal. I bought a totaled 2007 Prius. I used the brake actuator from it only at first in my 2005. Same problem. I then replaced the Ebay skid control ECU with the one from the 2007. The brakes are working great now. Apparently the brake actuator and skid control unit need to be formally introduced to each other. Either by a Toyota dealership or the pin jumper on the OBD2 plug and leave the car on for 30 minutes. Mine works now. That's my guess. Also, my original brake actuator part number was not the same part number as the 2007 donor car.

 

I don't think that's the case. It is, however, necessary to perform "initialization of linear solenoid valve and calibration" when the skid control ECU, brake actuator, or brake pedal stroke sensor is replaced.

 

Then why did mine work only after replacing both skid ecu and brake actuator from the same donor car? They were obviously already "calibrated"/ initialized/ ("formerly introduced to each other": layman's terms) to each other.

 

It's possible we just don't know what exactly happened while you were doing this work on your car, and haven't got enough information (not even the trouble codes) to piece it together after the fact.

On the other hand, making up an explanation that has no connection to what the repair manual tells us about how the parts work, just for the sake of a satisfying story, only means ... we still don't know.

 

I am having the same problem. First 2 seconds after starting the breaks don’t work. Breaks work fine after driving though. Did you find a solution?

 

On the face of it, your brake problem might seem like you're 'having the same problem' but to be certain you need to read your codes. If you have your DTCs and can share them here, we can give much better advice to fix your problem.

If you don't have a code reader here is a thread that discusses some that are reasonably affordable with a summary in post #37

While you wait for your code reader to arrive, you can learn how to blink out engine and brake codes on the dash warning lights here: Blink (a/k/a Flash) Codes – How to.