Prius brake system failure - Fuel Economy, Hypermiling, EcoModding News and Forum

redpoint5 · 09-15-2016, 09:18 PM

I just started my PiP after fully charging it, hooked up a small trailer and plugged in the pigtail. Then I moved the car 200 ft along the curb and parked. Realizing that I need to move forward a few more feet, I attempted to start the vehicle, but the brake pedal travels all the way to the floor, I have a traction control error, and the display says I need to depress the brake pedal to start. I've disconnected the trailer pigtail and tried starting a dozen times, with no success.

The brake booster is making noise letting me know it's building up pressure, but the pedal travels to the floor. Brake fluid is right near the max, and nothing has been done to introduce air into the system.

What could be the cause of the braking system failure? I'm hoping to leave in 2 hours, so I'm anxious to get to the bottom of this.

Ecky · 09-15-2016, 10:26 PM

Did some googling, and I'm getting the impression that the transition from electrical to mechanical braking isn't... well, mechanical, like it is in Honda's hybrids, but that the ABS ECU controls that. This might be a software problem, and if so, you may not be able to fix it without a Toyota dealer.

LittleBlackDuck · 09-16-2016, 01:59 AM

Only way to know is to read out the codes using Toyota Techstream or similar.

Simon

redpoint5 · 09-16-2016, 03:06 AM

Whew, just a fuse. Thought it was good because I checked the rear light fuse, but the one that was blown said brake on it. Not sure if that is the fuse for the brake system, or for the brake lights. I'll check for shorts in the trailer tomorrow.

The Traction Control light is still illuminated, so the car isn't entirely happy yet.

redpoint5 · 09-16-2016, 03:07 AM

Whew, just a fuse. Thought it was good because I checked the rear light fuse, but the one that was blown said brake on it. Not sure if that is the fuse for the brake system, or for the brake lights. I'll check for shorts in the trailer tomorrow.

The Traction Control light is still illuminated, so the car isn't entirely happy yet.

LittleBlackDuck · 09-16-2016, 04:25 AM

Quote:

Originally Posted by redpoint5

Whew, just a fuse. Thought it was good because I checked the rear light fuse, but the one that was blown said brake on it. Not sure if that is the fuse for the brake system, or for the brake lights. I'll check for shorts in the trailer tomorrow.

The Traction Control light is still illuminated, so the car isn't entirely happy yet.

I think you will find that after a few successful start-stop cycles of the hybrid system the light may go off but a code will still be registered with freeze frame data. I bought a cheap Chinese cable with a "copy" of tech stream from eBay to read and reset these things. Cost about $40 if I recall. I recommend you do the same. It also allows you to see battery voltages and lots more interesting stuff.

Simon

redpoint5 · 09-16-2016, 06:43 AM

Thanks for the quick responses.

I have Techstream and cable, but don't have my 32 bit laptop handy. I've been unable to get it to work on a 64 bit system, although I could set up a VM. Didn't have time to do that today though.

I'm monitoring most everything with Torque Pro.

LittleBlackDuck · 09-16-2016, 08:05 AM

Quote:

Originally Posted by redpoint5

Thanks for the quick responses.

I have Techstream and cable, but don't have my 32 bit laptop handy. I've been unable to get it to work on a 64 bit system, although I could set up a VM. Didn't have time to do that today though.

I'm monitoring most everything with Torque Pro.

All good. Curious which fuse. I have a CT200h which has almost the same drivetrain.

Simon