2005 Prius brake code and calibration failure

Hello,

I have spent a bit of time here since buying my daughter a 2005 Prius touring a few years back. I'm no mechanical whiz but I can follow directions and do my own brakes, oil changes, rebuilding of HV battery pack etc. So last week my daughter comes to me with " there's something wrong with my brakes". Turns out all 3 of her brake lights are on. There's no actual braking issues on practice while driving and the pads rotors, bearings, calipers, wheels, tires, etc are in decent shape.

After checking here brakes myself. I got busy online and found the "test mode procedures" for pulling the abs codes (I don't have anything more complex than an ELM based OBD2 Bluetooth thingy for interactions with the computer). Since I can't pull serious codes or monitor most realtime data, I counted the lights and at the end of the day I my problem is "linear solenoid valve offset unlearned". I also learned how to clear the brake system codes by jumping a different pin to ground and tried that. The codes cleared for about a week and then came back. There were 3 codes total, but two of them only said to "look at the ecb light".

I found the procedure to recalibrate this and tried it multiple times, but after 30-45 seconds the front brakes make a semi-loud popping sound (after a series of less loud pulses) and all the brake lights go back to "just on". No changes in flashing speed or anything. While the brakes are obviously doing their thing, the VSC and ABS lights are flashing very fast and the ECB light is flashing very slow. At the exact moment of the pop they all go to solid on and the codes remain. I've done the manual erasure of the data (which I presume isn't there anyway) between attempts to calibrate and it makes no difference.

So, I'm wondering what I can do further before I try and shell out for a new brake actuator. I'm about to (as soon as I finish typing this) connect the 12v system to my own car and attempt the calibration again. The Toyota info on the procedure says that 12v battery plays a relatively big part in the speed of the procedure and I found a couple people who said that a weak battery made their Prius fail. I have tested the battery and all it's connections and it seems totally fine. I'm also a bit unclear on exactly how level the car needs to be and how straight the wheel needs to be or if either of those will make the calibration fail part of the way through. I don't have any very scientific way to measure either, but I have paid close attention to the wheel and also moved the car to a brand new parking lot in my neighborhood.

It seems like I would have other brake system codes if there was a major failure in the system so I don't want to jump at buying parts that I can't verify are broken.

Any help is appreciated.

JJ

 

Hello hello. Sorry for the delay. The clicking is in the right front caliper and to a lesser extent the front left. It starts with the back brakes and then moves to the front while still doing something in the back. The volume and mechanical vibration steps up each time until it stops. The pop seems like it's in the front brakes as well. I haven't tried to stethoscope the brake system under the hood as this happens.

I took the wheels off to check for any odd mechanical stuff and to clean everything and tried the offset again. Fails the same way, but I touched everything in the wheel well while it tried. Not hearing any noticeable noises coming from anywhere but the brake calipers/ drums.

The pop sound is at the exact moment that all the lights stop flashing and go back to normal. I could try and make a video in the next couple days if any of you are interested. I haven't gotten a pressure meter out to see if there are any strange readings during the calibration. My brother in law sent me the service manual but I think he may have left out the bit that covers this. So far I've been working with what I can scrounge up online.

 

As far as bleeding goes, I wouldn't be able to do anything besides regular old brake bleeding as I don't have access to a "real" scan tool. Hopefully my brother in law will find me someone who will let me use theirs.

I'm trying to put off buying a super expensive part until I know that it's really bad and there's not something even worse happening. I'm okay with doing the swap if that's the solve though.

There have been no brake issues and no brake work on this car for at least 3 years. Is there a chance that there could have been air in the system all this time? I'm also a bit fuzzy on how the calibration data was lost in the first place as there was no new work done to the car.

 

So I'm going to order a mini vci clone so I can attempt to run techstream and monitor things in realtime while I search for a brake actuator that isn't 1200$. There are while Priuses available for 1200-1400. Are these Chinese knockoffs capable of realtime data back and forth? I can't find any reliable info on what's supported and what, if anything, isn't. I figure it's worth 30 bucks or whatever.

The car has now been examined and the brakes cleaned and serviced in a more thorough fashion. Everything points to the actuator being bad, but it seems silly that there's no other codes coming up in the brake system. The engine in my daughter's car is kinda rough to be dumping tons of money into it at this point. Is there anything else I should be doing?