Invalid mode vs. Battery disconnect

disconnect negative terminal.

 

Just keep the key fob at LEAST 20 feet from the car and you won't have a problem.

 

Invalid mode allows for bleeding the brakes.

See the below video for what you are about to do:

Nutz About Bolts Prius Maintenance Videos

Videos 18-20.

Good luck and keep us posted .

 

Can't bleed the rear brakes with the 12v battery disconnected.
Keep the fob away until you completed the rear pad replacement and cleaning of the pins.
Then you can do the bleeding per the videos.

 

Is it possible to bleed the front brakes with the battery connected?

Also, in invalid mode, if you move the steering wheel will it knock it out of invalid mode?

I've bleed many brakes before, but I'm deathly afraid of doing this due to the chance of receiving an error once all is said and done. I'd like some way to clear if needed. Suggestions welcome.

 

Fronts are the same as any car.
Rears you either need techstream, or have someone in the drivers seat, press the pedal while someone
opens the bleeder. You can reset the code if you get one. Just don't let the fluid run out of the reservior.
I'm not sure about the steering.

 

I think there are two different ways to get into "invalid mode", one using Techstream, one using a chicken dance.

My experience is that asking for invalid mode through Techstream sets a C1451 code, which you also need Techstream to clear. But I never hear about that happening to people who went into invalid mode by way of the chicken dance. So that might be less overall trouble.

If you don't have another person to hold the pedal while bleeding the rears, you can use an official Brake Rock.

 

Thanks! Btw, I meant can you bleed the fronts with the battery disconnected. Wondering if I can get away with bleeding the fronts and then doing the whole techstream thing on only the backs. I'm guessing it will throw an error code. While I do have an OBD scanner, I don't think it is capable of clearing brake trouble codes: Ancel AD310.

 

Yes, the front brake are normal power vacuumed assisted brakes as any car that is not a hybrid.
The rears are electric.
nutzaboutbolts has a video of how to do it without techstream.

 

For pulling the calipers off the rotors: disconnect 12 volt neg cable. Leave it off till done, and push the brake pedal several times as a final step, before reconnecting.

For brake fluid replacement: invalid mode. And read carefully the list of do's and don'ts. For example, don't turn a wheel while it's invalid mode, it'll kick you out of the mode.

Definitely watch @NutzAboutBolts videos, on both topics.

 

There is no vacuum assist in the Prius brake system anywhere. The power assist comes from brake fluid pumped into an accumulator to high (positive) pressure by an electric pump.

 

That has been on my mind all day. I remember reading somewhere that the Prius is NOT vacuumed assisted.
I was just too busy today to go check it out! Thanks!

 

Thanks correcting that misinformation!

 

How does that duplicate invalid mode and what is invalid mode anyway? Thanks

 

Invalid mode is explained in the first attachment in post #11. It's necessary to use techstream or invalid mode when bleeding the brakes. Either will do. Text from the attachment:

Select ECB (Electronically Controlled Brake system) Invalid Mode.
(1) Perform the procedure listed below in 1 minute.
1. Turn the power switch on (IG) with park (P) selected and parking brake applied.
2. Select N and then depress the brake pedal more than 8 times in 5 seconds.
3. Push the P position switch and then depress the brake pedal more than 8 times in 5 seconds.
4. Select N and then depress the brake pedal more than 8 times in 5 seconds.
5. Push the P position switch.
(2) Check that the brake warning light / yellow is blinking.

Translation, a little more literal:

1. Ensure parking brake is set, then within one minute:
2. Push start button twice without foot on brake.
3. Depress brake pedal and shift to N.
4.Depress brake pedal 8 times within 5 seconds.
5. Push park button.
6. Depress brake pedal 8 times within 5 seconds.
7. Depress brake pedal and shift to N.
8. Depress brake pedal 8 times within 5 seconds.
9. Push park button.
10. Confirm invalid mode achieved by brake warning light blinking.

 

Thanks I will read up

If you keep the key fob a good distance from the car when doing maintenance will this duplicate invalid mode?

 

Not a chance.

 

In fact, am I assuming correctly that you'd need the fob in the car for the dance to work?

 

By the way, the front brakes are served by two separate hydraulic circuits, one for normal operation, one for fail safe. You'll notice if you follow the bleeding procedure in the manual that you do each front caliper twice. One time, it is like bleeding a conventional car, where you force fluid out by pumping the pedal. The other time, it is just like the rears, where you open the bleeder and the fluid flows right out under accumulator pressure. That happens because Techstream commands the right valves to open for that part of the sequence. If you are not following that sequence when you bleed the fronts, that entire separate hydraulic circuit never gets bled.