Red Brake, ABS, VSC, and (!) Illuminated Troubleshooting

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by KaylaP, May 1, 2021.

  1. KaylaP

    KaylaP New Member

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    Vehicle:
    2009 Prius
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    Three Touring
    Hi All,

    I’ve been a reader of these forums for a few months now. They helped me make the decision to purchase a Prius. This is my first time posting. A little background about my Prius:

    It’s a 2009 Prius Touring. I purchased it in November 2020 with 145k miles. It now has 165k miles. Upon purchase (at 145k miles), I replaced the spark plugs (had never been replaced), the engine water pump (had a small leak coming from the weep hole), and the rear struts (were leaking). I also cleaned the hybrid battery fan when I replaced the rear struts just because it was convenient to do so and had never been done. Since those repairs, I haven’t had to do anything to the vehicle aside from oil changes, tire rotations, and filter changes.

    I use this vehicle primarily to do food delivery. I also have a fleet of gen 3’s that I rent out. So anyways, yesterday was an exceptionally hot day in SoCal - low 90’s in my area when we are typically in the low-to-mid 70’s. I began driving around 4:00 in the afternoon. I typically drive 8-10 hours straight. About 2 hours into my drive, I noticed that the red parking brake indicator on the dash was displaying on and off when the parking brake was not engaged. About an hour later, the red brake light started staying illuminated constantly. I made nothing of it, just assuming that maybe a sensor in the parking brake assembly was malfunctioning. However approximately 4 hours after the light started staying on permanently, I was driving about 50 mph down the road and coming up to a red light. I began braking lightly to slow down, and the Prius lost traction for a split second and did a little jump type of movement. At this time, the ABS, VSC, and (!) lights became illuminated on the dash along with the red brake light. I lost all power to the brakes, but was still able to stop albeit not quickly. I was about 10 miles from home. I took surface streets very slowly and made it back to the house. Upon arrival at the house, I parked and attempted to scan the codes. Seeing as I only have a regular OBD2 scanner and not techstream, I was unable to pull any codes. I turned the car back on to move it into its parking space. The lights were still illuminated on the dash when I turned the car on. They briefly turned off but quickly re-illuminated, like within 20 feet of movement.

    This morning I went to look at the car again. I noticed that the brake fluid was quite low (about a half inch below the minimum mark). At this point, I topped off the brake fluid. It required approximately 10 fl. oz to be right below the maximum fill marker. I also checked the 12v battery as the car had sat overnight. With the ignition turned off, it read 12.05v. With ignition off and headlights turned on for a moment, it read 11.85v. With ignition on (ready mode), it read 13.8v. (I haven’t noticed any drop in fuel economy or dim headlights.) Additionally, I had read in another post that some owners experienced the same dash lights when their inverter coolant pump failed. I was able to hear the whine of the inverter coolant pump and see turbulence in the inverter coolant reservoir. When I put the car in ready mode to read the battery, I noticed that all the lights on the dashboard had disappeared. I engaged and disengaged the parking brake, and the red brake indicator performed as it should. I then drove the car around my neighborhood for about a half mile. The brakes had power, and no lights became illuminated on the dashboard. At this point, I decided to take the car down to a reputable Prius repair shop to have any codes read. They were unable to pull any data from the previous night. I drove around a little and then returned home. In total, I put around 40 miles on the car after topping off the brake fluid and having the dashboard lights disappear. The lights have not returned, and the brakes are performing normally.

    So my question is, does anyone have any insight as to what may have caused all those lights on my dashboard to illuminate? Could it all have been caused by low brake fluid? Is it possible that this will happen again? I’m obviously quite nervous to drive the car and lose power to the brakes. Any help would be greatly appreciated!

    -Kayla
     
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  2. Fred_H

    Fred_H Misoversimplifier

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    Hi Kayla, welcome to Priuschat! Thanks for the detailed description, that helps a lot.

    I think that you have described two different things going on: Firstly, the general brake warning light, which was most likely caused by the low brake fluid. Secondly, the ABS and VSC warning lights, which normally light up briefly when the ABS and/or VSC is activated because of a slipping or bouncing wheel.

    The brake fluid reservoir has a sensor that should light up the brake warning light before the fluid level is dangerously low. The brake fluid level normally goes down gradually as the brake pads wear and the brake pistons extend further out of the cylinders, pulling more brake fluid out of the reservoir, and into the cylinders. Normally the brake fluid shouldn't drop so far just from brake pad wear unless it wasn't completely full to begin with. So look for brake fluid leaks, and check brake pad thickness.

    ABS can be activated by a wheel slipping so slightly that you don't even notice the slippage before the ABS kicks in. Sometimes just a little sand or oil on the road can trigger it. When that happens, the regenerative braking cuts out abruptly, and sometimes it takes a second before the friction brakes start gripping. That is normal, but then when you brake again later, it should brake normally again.

    If the brake fluid level was so low that the brake pump and pressure tank were starved of fluid, then you would have had to press the brake pedal much, much harder than normal. If that was the case, then it might be a good precaution to have the braking system bled to make sure that there are no air bubbles in the system.

    In most cases, when a recognized error goes away, after a certain interval the error code is erased from the current error code list, and stored in the error code history list. I'm not sure if that is also the case with low brake fluid, but you might want to double check the error codes stored under history, using the Toyota Techstream diagnostic software.

    I hope some of the many Priuschatters more knowledgeable than I will also reply to confirm or contradict. Till then please keep an eye on the brake fluid level.
     
  3. ChapmanF

    ChapmanF Senior Member

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    It can be useful to have a short piece of wire in the car that you can use to retrieve the brake system trouble codes right away if those lights come back on. Takes the "what if my OBD reader couldn't get the codes" or the "shop says they didn't get any codes later" complications out of the picture. You use the short piece of wire to connect the Tc and CG terminals at the car's diagnostic connector, and then count blinks of those dash lights, to get two-digit codes. There are other threads about this.

    Doesn't give you all the information Techstream would, but way better than not having any.

    In the big picture, all four of those dash lights in your title are controlled by the same ECU in the car; it's divided into different functional groups the lights correspond to, and they tell tales on each other, so it's super common to get those lights coming on together.

    Usually, when you pull the blink codes, the codes on one of the lights will be telling you something interesting, and the other ones will be blinking codes for "hey, go look at that one."
     
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  4. KaylaP

    KaylaP New Member

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    Three Touring
    Hi Fred, thanks for the reply! The brake fluid reservoir was lower than it should have been, but not completely empty. When all power to the brakes cut out I basically had to floor the brakes in order to stop the car. Also, strangely you mention how when ABS is activated the regen braking cuts out abruptly but then returns to normal braking later. It required an overnight park and a brake fluid top off to begin braking normally.

    Looking at my pads, they aren’t brand new but definitely not thin enough to necessitate replacement. I was thinking along those same lines that perhaps I have a brake fluid leak somewhere. My levels haven’t dropped in the past 2 days since I topped it off. But I suppose a brake fluid leak wouldn’t be that easily apparent, would it? Would it leak slowly over time or if I had a leak would I be able to see it within a couple days of topping off?
     
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  5. KaylaP

    KaylaP New Member

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    2009 Prius
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    Three Touring
    Ahhhh! The revered sage Chapman! I must say I’ve seen many of your replies on these forums, and it is an absolute honor to have someone as knowledgeable as yourself comment on my post!

    I have definitely made sure to keep my OBD scanner and some wire in the glove compartment should those codes return. Unfortunately, I didn’t know anything about that method until I stumbled upon it on PriusChat after the codes had disappeared.

    I now see that I really need to make the small investment in techstream. Would be an invaluable tool to have in figuring out these problems. It was inconvenient that the shop “couldn’t find any history of codes”. They said they could take the car in for an inspection and figure it out, but of course that would cost more. I’ve always had a distrust for the hybrid specialty shops especially in my area. They seem to charge an arm and a leg for work that just doesn’t meet my standard for quality. For this reason, I’ve always opted to do all my own maintenance.

    As of now, I’ve put around 200 miles on the car and the lights have not returned. Seeing as how my red brake light began illuminating first, I’m kind of treating that as an early warning sign. It hasn’t returned yet, but if it does I’ll know something bad is coming. Thanks again for the advice and info!
     
  6. ChapmanF

    ChapmanF Senior Member

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    That is kind of worth a further look. The fluid should be at MAX when two things are true: (1) the brake pad thicknesses are all factory new, and (2) the brake system is "zeroed down".

    What does (2) mean? Well, the system has a pressure chamber in it, filled up by a pump. If you have started the car (or even just opened the driver's door), the system pumps that chamber up to pressure, using fluid from the reservoir, and so the reservoir level drops. "Zeroed down" is the condition where the pressure chamber is depressurized and that fluid is returned to the reservoir so you can judge the level.

    If you have Techstream, there's a utility in there where you ask it to zero down, you hear a click-whooosshhh, and the reservoir level rises; that's where you should be checking the level. Then if you start the car, or tickle the driver's door switch, you hear the brake pump run and you can watch that level drop again.

    So it's natural for it to look a little low, if it isn't zeroed down when you look.

    The other thing that makes the level lower over time is wear of the front brake pads. The thinner they get, the more the caliper pistons extend, and the more of the system's fluid is staying there in the calipers. In principle, if there have been no leaks, whenever you get around to replacing front pads, you smush the pistons back into the calipers, and the reservoir level goes right back to where it left the factory.

    The rear brakes on a Gen 2 don't work that way; they have mechanical adjusters that compensate for their wear, so they don't end up holding extra fluid as the linings get thin. (Gen 3 and later have calipers on the rear, so their lining wear does drop the fluid level, just like the fronts.)

    So the lowest you should ever see the brake fluid is when (1) the system isn't zeroed down, and (2) the front pads are near end-of-life. If you say your front pads are still pretty thick, but you saw half an inch below MIN, I would consider checking for fluid leaving the system anywhere.

    If you have Techstream, one thing you can do is turn the car on, sit in the driver's seat, stand on the brake pedal pretty hard, and watch the pressures on the four brake lines. If you see one that isn't holding steadily high, but is slowly dropping and getting nudged back up (you might hear soft click near the firewall for each nudge), that would be a line and wheel cylinder to go inspect carefully for any wet areas.

    I once had an older vehicle where a rear brake line rusted and developed a split, and only the highest brake pressures, from really pressing the pedal, would open the split and make it squirt. The wet area was on the other side of the underbody from where the line was. (Those lines didn't have the plastic anti-rust coating Toyota's lines have.)

    By the way, if you ever suspect such a thing, don't go trying to find it in person (say, risking your eyes or other body parts while a friend holds down the brake). A jet of fluid at that pressure can go right inside skin, and make injuries that emergency docs sometimes underestimate, then they turn gruesome later. I caught the one in my old vehicle using a good light, an inspection camera, a strategically-draped shop towel, and watching the camera video from inside while I stepped on the brake.
     
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