Urgent Help!!! Braking problem with Prius 2010

Have you driven with ABS before? The ABS (Antilock Braking System) can feel odd as well. When I taught my son to drive (last child, first car with ABS), I had him try a full-emergency brake on a deserted road - tarmac, wet and on loose surface. That car (20 yrs ago, VOLVO) gave a quite noisy banging as it "brake-release-brake-release" etc, and on that car, you could feel it release the brake when it started to skid. His first reaction was to release the brake himself when he heard the noise, even though I'd warned him. It took a couple of tries for him to become confident. My later cars haven't been as noisy and obviously modulating the braking as that car.

 

Note that when this is the correct explanation, it happens only when starting from regen-only braking, which can only be light to moderate (depending on speed). This switchover-delay mechanism doesn't happen when starting from friction braking, which covers all hard braking at all speeds.

If this type of incident happens under hard braking, then something else is happening.

 

I have the same exact issue. The car jumps forward if I hit a bump or pothole while braking. It loses the brakes for the moment which I think is a severe safety issue. The sad part is, my car wasn't even part of the brake recall so I can't do anything about it, but just live with it..

 

The switchover-delay mechanism described above happens only under light to moderate braking, not hard or panic braking.

If you are using light to moderate braking, you are not yet in a severe safety situation. For such situations, you would be going directly to hard or panic braking, bypassing this issue. You would not be wasting time and braking space on light braking.

Verify that the recall has been performed, get it done if it was missed. But note that the recall does not eliminate the issue, just reduces it.

 

For more details about the recall: POLL: Did the ECU Update Recall work for you? | PriusChat

I found it requires: (1) slippery road surface; (2) moderate braking; (3) speed ~18 mph (~30 kph) and; (4) significant bump or pot hole 3" (7 cm) deep. After the brake controller software upgrade, I could not replicate the symptom but I understand others have in different conditions. It is surprising the first time.

Bob Wilson

 

Over here, we take it to a dealer and they check the car and Toyota's databases.

 

Would be nice if you could enter a VIN on a website, in any country, and get critical recall status for the vehicle.

 

This seems to be a common problem with 3Rd Gen or at least 2010, my car (2010) has the same problem. I have got used to it.

 

Another question:

Does your issue approximately fit Bob's description in post #29? In particular, does it seem limited to light to moderate braking and low speeds? If so, then I'd be comfortable writing it off has the normal Prius quirk, which is mostly a consequence of using regenerative braking in applicable conditions and having to switch to friction braking when road conditions deteriorate. Most of us just go accustomed to it. It wasn't a real safety issue because it wasn't popping up in hard braking.

If your issue occurs in other conditions, harder braking or highway speeds, then my concern that something different is happening would rise very sharply.

 

VSC I think Vehicle Stability Control (you may get a better answer) but basically try to avoid slipping/slidding.

It is your perception ONLY that it accelerates ... long known issue ...

Let me suggest an easy demonstration. Some place where it is safe and straight drive somewhere around 40 mph start breaking semi firmly and at the same time change to N you will feel the regen breaking disengage and the friction break kick in ... you will FEEL a cut out of breaking for a moment and you perceive that it was accelerating but it at most wasn't breaking for a fraction of a second.

It is unusual for all new prius owner.

 

I feel it occasionally even AFTER brake control sw upgrade (certainly less fequent). My guess you just got used to it. See my suggestion above how to demonstrate and PROVE to new prius driver what is happening.

 

Now I agree about this description but it doesn't fit in my usual practices:

Some place where it is safe and straight drive somewhere around 40 mph start breaking semi firmly and at the same time change to N you will feel the regen breaking disengage and the friction break kick in … you will FEEL a cut out of breaking for a moment and you perceive that it was accelerating but it at most wasn't breaking for a fraction of a second.
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I regularly use "N" for coasting and frequently shift to "D" and on steep hills, "B", when needing to slow down. It is rare but occasionally while in "N", I'll have to deal with traffic or something unexpected that involves braking and at the same time, shift into "D". For me, already braking in "D" or "B" and shifting into "N" would be counter to my usual practice. Regardless, your description makes sense.

Bob Wilson

 

Understood !!!

I KNOW that you KNOW what is going on I suggested this to OP ... to see what is happening ... this is NOT ABS this a "strange" phenomena (prius) is that in "normal/average" breaking is regen BUT VSC/ABS only works with physical breaking (I assume) so system tries to switch. And unaccustomed user thinks the car accelerate when it doesnt.

 

I have the same exact issue in my 2010 JDM. However I noticed that EVSE does not indicate when the incident happens. Therefore, it should not be the EVSC. I have recently change the ABS modulator. Originally it had a EA model but had to replace with EB. As per my memory, this was begun after the change. Anyone can help me on this please..

 

Welcome. Can you please, spell out:

JDM
EVSE
EVSC
ABS (this is I know, but anyway)
EA
EB

 

Probably EVSC is referring to the Electronic Stability Control. EVSE sounds like it refer to the Event Data Recorder.

It could be described differently in the Sri-Lanka Owner's Manual, and JDM could be a local model description - same as Australia hasn't got any of the US/Canada model descriptions (or some colours).