Brake issues

Sounds like a basic hydraulic problem that a good brake inspection should id. Failing a solution there, your brake by wire booster/master cylinder/abs/brake-ecu would be suspect. However it is far more likely to throw codes.

 

Does the ABS warning light work normally went you furst turn the car on? (ie, comes on as a "bulb test" then turns off).

Sounds like you should begin with a complete inspection of all the base braking system components - pads rotors calipets and hoses - as well as the rear brakes. Look for obvious stuff like rusted or seized caliper pins or pads stuck in the brackets. Also should have the car in neutral and have someone lightly press on the brakes and see if the left front applies at the same rate as the right.

If any wheel is locking up without the ABS light activating, I might wonder what's going on with the system, might need Techstream to look at ecu data to figure it out.

Posted via the PriusChat mobile app.

 

At 250,000 miles - the first question should be "what service have the brakes had in the past quarter-million miles?"

Sounds like the LF wheel brake is doing nothing, and/or the RF wheel brake is "grabbing".

Pulling off the front front wheels and looking at the discs, pads, and calipers may answer your question.

Once you've addressed the most obvious things - then you can dig into the esoteric stuff like p[inched hydraulic lines and the like.

I am curious what's going on with the ABS - but you need to have a basically function brake system before you can do much with that.

 

I'm kind of wondering whether the electronically controlled brakes are operating at all.

If the system is fully in hydraulic fail-safe mode, that only works the front brakes, which would explain the rears being out of the game, and from there it only takes a problem with the LF caliper to leave all the braking to be done with the RF.

Ordinarily that would lead to a bunch of dash lights, but the funky relay situation already suggests the DPO might have noticed some issue with the brakes, and taken some steps to suppress the usual warnings. I'm not positive, but it's possible (I knew somebody with an old SUV who decided "I used to drive cars without ABS anyway" and decided not to fix them, and just drove it that way for years).

If it were my car, I might start by trying to get the blink codes from the brake ECU. If you can. That would quickly indicate which dash lights do or don't work, and whether the ECU is alive and responding and has anything to tell you.

If it really has been doing fail-safe mode for who-knows-how-long, the rear brakes probably haven't moved in a while and may need some old-fashioned elbow grease to get working again, and the same may apply to the LF caliper, whatever the reason is that it isn't doing its share.

So part of this puzzle will definitely involve getting the wheels off and taking a look down there.

 

^This.

Toyota USA recommends an in-depth brake inspection every 30K miles or 3 years, whichever comes first. It's spelled out, albeit pretty subtly*, in the Warranty and Maintenance Booklet; a paper copy came with the car when new, and you can download pdf versions from Toyota Tech Info (and "Toyota Owner's" site?)

Toyota USA says nothing about brake fluid change, but Toyota Canada says tri-yearlly or 48K kms, whichever comes first.

* Every 5k miles (or 6 months) says to "visually inspect" the brakes, which presumably takes place during wheel rotation. But at 30K, 60K and so on, they omit the "visually inspect" phrase, and instead mention inspection of "Brake linings/drums and brake pads/discs": It is very ambiguous, but you can glean they want you to get serious every 30K:

 

I am still thinking this car may have a basic electrical issue going on, which would be kind of orthogonal to anything you would learn from the recommended physical brake inspections.

 

I might consider NOT replacing the rear brakes until you have some direction on the rest of the system (don't add another variable to the equation) . The rear brakes do maybe 20% of the stopping on a front wheel drive car like this. If you have at least 1 mm of lining on the shoes , that's good enough short term.

Maybe adjust them if needed- the self adjusters often do not self adjust. As long as the brakes don't drag afterwards.

Now on your dash, press the power button twice without pressing on the brake pedal. Tell us all the warning lights that you see on the dashboard, to the left and right of the speedometer.

Posted via the PriusChat mobile app.

 

Or just post a pic.

 

There's enchroaching rust on the rotors, into the area swept by the pads. Not terrible, but might want to spring for new rotors; if they're original, 250K miles is a lot.

addendum: pic of ours (2010, gen 3), around 90k kms, and pampered west coast BC. Cobwebs hmm…, it hasn’t been that long, energetic spiders?



Second gen brake info, including rotor specs, in attachment. With a dial indicator (with magnetic base) and 0~25 mm micrometer, you can check against spec. Still, new rotors probably simplest/cheapest, at this time. Brake bleed info attached too, might help.

 

Replacing brake fluid and bleeding brakes on a GEN II Prius without Techstream | PriusChat

Moisture in the brake fluid can cause similar problems with your braking system as well. Bleeding the brakes on the gen 2 without techstream is a pain in the butt(I just did it a few weeks ago), but it's not more than a two man two beer job. It should only take you about 90 minutes.

This is a quick and cheap process to eliminate one of your variables.

Also, if you noted your bluetooth scanner was having connection issues.
Hybrid battery diagnostic and repair tool for Toyota and Lexus (priusapp.com)
click on the "what obd2 to buy" I purchased one from amazon through one of the links provided. Was in hand in two days and worked great with the DrPrius app (I think the one I purchased was about $13, well worth it).

 

@Gotsqueeze2345 Not sure if this will be helpful to your situation, but here's my saga of replacing my brake actuator: Need advice: Brake, (!), ABS, VSC lights on | PriusChat. Part way through this process, I removed a bad replacement actuator I got on eBay with the original brake actuator (which was going bad). Given I had removed/replaced actuators twice at this point, there surely was air all throughout the system that shouldn't be there. I didn't have Techstream at the time, so I tried doing a non-Techstream brake bleed process that was posted on PriusChat (I think someone else linked it above).

Then I took the car for a test drive, and the brakes were totally wacky, notably including the left front tire locking up for no particular reason... which is what you seem to be describing.

I eventually replaced the original brake actuator with a brand new one, then ran the full Techstream bleeding and initialization procedures. The Techstream bleeding process is really long, runs various solenoids, and has lots of steps to bleed the entire system. After all this, my brakes are back to normal.

So perhaps you have air in weird places in the brake system... or your brake actuator is going bad.

Maybe you could try using Techstream to run a proper full brake bleed process.

 

Just as an additional note, bleeding the brakes the non techstream way simply required re-initializing the diagnostic mode several times throughout the procedure. If you have any experience bleeding brakes it's actually quite simple. My 2005 Prius with only 132k miles on it had horrible brake fluid in the lines. I'm quite glad I screwed up the rear drum install(didn't get the spring on the shoes quite all the way and ended up having springs, shoes and clips all over the driveway(many colorful words were heard to the heavens) which forced me to bleed the brakes. I was kind of shocked the fluid was in such bad shape(I've purchased used vehicles much older with more miles and not seen such awful looking fluid). Given the mileage I wouldn't hesitate to essentially do a full service on the vehicle.