I recently had an ABS issue after I incorrectly flushed the brake fluid in my gen 2 Prius, 2009. Well I reset the ABS system myself (there is an online hack on how to do this), no more ABS issue, but ever since my hybrid battery is charging more than it did before, in a concerning way. When looking at the "Energy Monitor" screen on the main console (with audio, climate control act), the battery on the screen used to regularly drop to 2 or 3 bars, but now the lowest it drops is 1 bar down from fully charged, so essentially fully charged. The battery now regularly displays in the green, where all bars on the battery are full. On the highway it drops 1 bar for parts of the drip, or in town, but quickly goes back up to 100% charged being displayed when coming from the offramp, or going down hills. This concerns me since I don't want the battery to overcharge, and I have always been told you don't want the battery to stay fully charged (which it is often now), or the opposite, low at 1 bar too long either. Any ideas on why this would have occurred, and what I might do to normalize the charging of the hybrid battery?
Full charge in Prius OEM is ~80% You got nothing to worry about, especially with NiMH electrolyte, even at 101% charge levels!
Thanks for the reply, but being at 100% full like 60-80% of the time isnt concerning? Or that shortly after going downhill, or braking, it stays at 100% fully charged for like 5-10 minutes?
It is not 100% fully charged. To reiterate what PriusCamper said in post #2, The graphic on the Energy Monitor screen only displays the 40% (the bottom purple bar) to 80% (the top green bar) range of the battery. You should also understand that when the top bar lights, it does not mean your battery at 80% charge as this will light when the SoC is 75% and continue to accept charge until it reaches 80%. Furthermore, the second bar has an approximate range of 64% to 77%. From this you can see that the battery can never reach 100% from in-car charging. The change in behavior you describe is typical after the battery has been reconditioned, or sometimes after the 12 V battery has been disconnected (or gone flat). If that has not happened, I'm not sure what could explain the change in behavior. In any case, it is nothing to worry about, as Camper said.
Because "reset the ABS system" is not a thing, a post like this is a lot more useful if you link exactly what "online hack" you found that made you think it was—that way, other people reading have the best chance of knowing what you actually did.
If the OP can read the pack voltages with Techstream or some OBD2 dongle that might (but probably won't) show something interesting. If the sense voltages stick at 16V or higher, in normal driving on a flat surface, that would indicate that the car is charging the NiMH pretty much all the time. But if that was the case the display on the MFD should also show arrows directed into the pack, possibly even when accelerating with all green bars, which really shouldn't ever happen. Normally any acceleration on a flat surface will have the arrows moving away from the pack, with the exception of when the pack is nearly depleted, in which case the car may charge the pack even when though the driver is calling for it to accelerate. But I'm getting ahead of the data, which in all likelihood will be unremarkable.
Thanks for the response! Here is a link to the "hack", numerous youtube videos showing people doing it, and it did work for me. Title of youtube video if want to search for it is " Toyota Prius ABS Reset Brake Problem" In my own words, I am no means a mechanic or expert here, so Im sure my terminology sucks, but here is the "hack". You take a paper clip or some wire, put it in two of the 0BD2 pin holes (4th hole top and 5th hole bottom). After this hit the brake and the power button, a particular screen pops up, as soon as this screen pops up hit the brake 8 times under 5 seconds. once you do this, you should see the ABS lights turn off, or some change on the dashboard or screen. Turn the car off, and it should resolve the issue. For me this did the trick, my ABS system was not working, and spongy breaks making car very very dangerous. Only issue is my battery appears to be charging more than previously, that is the only change I see. Appreciate
This is also the method you use to read the blink codes... As in count the cycle of short blinks and long blinks and that count points to the problem your brake system is having. This "hack" is the last step in the process after you get your blink codes and you clear the error codes, but it doesn't prevent the error codes from coming back soon as the computers/sensors notice it again.
Ive driven about 180 miles since I performed this clearing of the ABS system. Wouldnt the codes come back on by this point, or my braking would be compromised if an actual issue was present in the ABS system? Originally this only occurred following a brake fluid flush I was doing, but I didnt realize a prius had unique instructions, compared to the typical gas powered car. So clearly I threw a code in the ABS system in flushing the brake fluid incorrectly, since was never an issue until I did the process wrong.
Depending on the error codes certain systems may be disable until the error codes are cleared. Eventually they'll come back. As for the jumping the pins "hack" and pushing brake pedal 8 times to clear codes after getting blink codes that's standard across most car designs: Blink (a/k/a Flash) Codes – How to. | PriusChat
The link you provided, very informative, thank you. That clarifies a lot. I was searching quite a bit prior to finding the youtube video, wish I would have seen this earlier, to better understand the situation. Im selling the car in two days for a very fair price to the buyer, I hope Im not setting this person up for failure. I was already planning on selling it, this just occurred prior to listing the car. I hate the thought of setting the future driver up for failure.
Oh yeah, that "hack". That's a code clear; just makes the brake/skid ECU forget what brake issue(s) it was trying to tell you about, and also forget what fail-safe measures it might have been taking because of them. This is not guaranteed to make the braking safer than it was before you did it. I see PriusCamper has pretty well covered that already. But other people do now and then come to PriusChat and read old threads, so this is worth emphasizing: If you're reading this thread and thinking about trying this "hack" to reset a brake issue, please start by reading this page: Blink (a/k/a Flash) Codes – How to. | PriusChat and be sure to scroll down to the "About clearing codes" part.
When the time is right let whoever buys it know about this PriusChat thread and we'll do our best to help them out.
Yes the "about clearing codes" section is needed, very helpful, though after the fact...... hah. Good to know its there though.
It wouldn't hurt if some of those other internet resources out there that keep sending people here thinking there's a "reset hack" (and probably sending other people with other cars to other car forums the same way) could have comments added—maybe even linking to the "about clearing codes" section on our wiki page. I can't easily go comment on that youtube video myself 'cause I don't have a youtube account. (I started creating one some years ago but got a few pages into reading their terms and conditions and said 'Nope.') But somebody who does have a login there could.
