It sounds like it must be the Brake Actuator/Booster, C1391

2013 Prius C
195k miles
Houston, TX
No major repairs
New NiMH battery as of Feb 2024
Significant FL quarter-panel damage from a side-swipe
Error code C1391

So about a week ago, the brake pedal lost almost all of its resistance while driving. I assumed master cylinder, but in researching, looks like for a Prius, it's actually the brake actuator/booster. [Master cylinder is contained inside the BA, I guess?]

I understand the code specifically identifies a detected leak/loss of pressure inside the unit. I also understand this could either be inside the actuator or the pump/accumulator.

I've watched a few videos, and the replacement doesn't look overly advanced. Tedious and long, but doable. It's the calibration at the end of the process that all of the DiY video-ers discourage for at-home repairs. Everyone says you really need to take this in to get it done. And that appears to mean anywhere from $1500-$4k, depending.

I've got a handful of questions:

• Is 200k nearing EoL for a Prius C?
• In anyone's opinion, is a likely $2k+ repair worth it, at this point? Or is this the beginning of a series of failures, now that my car is this old?
• Or... (and this is my hope... haven't had a car note in 8 years), do these little buggers typically chug along for 250k, like many Toyotas?

Or...

• Is this a doable repair in my driveway?
• If I buy a Techstream device, can a rank amateur work out the bleeding down and calibration of the brake lines?
• I see most Techstream devices are pretty friggin' expensive. Are there any devices that would accomplish this that aren't going to break my small bank?
• It looks like the parts (when bought through reputable sources) average about $1400 together. Any pro-tips on affordably sourcing these parts?

Thanks a ton for reading and helping!!
Grace and peace,
Matt

 

This is all really helpful. Thank you tons, Leadfoot.

I've got a buddy who's got a lot more shop experience than I do. We may tackle the replacement together. I've mostly been discouraged a bit about the price and the calibration stage. If I can justify the parts cost, I feel pretty decent about it. PriusChat always impresses me with how folks pretty consistently just throw it straight over the plate. If it's time to retire her, I trust I'll hear that here. Thanks for your counsel!

On this note, we had seen some commentary online that there are a ton of bogus "Techstream" products out there, and that the software they come with is pirated—and oftentimes untrustworthy. I checked Toyota's site, and it looks like the license I'd need is only available as a 2-day or yearly license, and for either $70 or $1360, respectively. That's wild. Any experience with the "pirated" versions out there? I'd love to feel confident in an inexpensive tool.

Matt

 

Yes! Doh! My bad. Unless I'm missing something, it doesn't look like I can edit the post to correct it.

 

Fair question! No, I haven't gotten a quote just for bleeding/calibrating the brakes after install. Those prices are what appear to be folks' real experience getting this whole replacement done professionally. I assumed it might not be safe driving it to a shop? Are you suggesting it's sufficiently safe to drive it a few miles afterwards? I've only ever done brakes on my truck and an old Honda, with a buddy pumping the brakes while I manned the bleeder valve. Pump it out; fresh brake fluid; pump all the air out; drive. Never had a calibration process to wrap it up, so I'm obviously really green.

Matt

 

You're correct! My bad! Apparently past the edit window, so I'll report it.

 

I got it! We use that down here in the states, too. I was responding to your initial post—and mis-reading it along the way! I read it as though you were asking if I'd gotten any quotes for the wrap-up, post-install.

I haven't taken it in, yet. The problem just started the weekend before last, and I've been doing some research in my spare time. Figured I'd get a general idea of what my options are before moving it out of the driveway. Definitely feeling like you're right: It's time to take her in for an estimate.

Curiously, for about 5 days, the brakes seemed to be functioning normally, and the instrument cluster cleared up. No lights, no codes. It's possible the app I'm using cleared the code—though I was deliberately NOT intending to clear it, myself. I know those codes are there for a reason, and it's often a bad idea to clear them without addressing the reason for the code to begin with. Anyway... made me think for a minute that maybe it was just a sensor issue, or something. But the 1391 and loosey-goosey brake pedal came back this past weekend, and she's sat there ever since.

Matt