ABS Warning Light Activating When I Hit a Bump while Braking

Yep, traction control, not VSC. The traction control on the Prius is quiet sensitive, and there is nothing you can do about it except learn to live with it. Toyota has toned it down just a bit, but it's still touchy. The big electric motor has so much low end torque you could spin the tires off without traction control.

Tom

 

I'll just follow up on this thread. I know that alot of owners have commented on how sensitive the various electronic nannies are in the Prius. I have rarely driven in a way that causes the VSC to engage, but when it does while cornering, I was somewhat surprised to find that it will actually increase the amount of steering effort to try to prevent you from decreasing the turn radius.
The worst two offenders are the ABS and traction control. As we are seeing more wet weather in Northern California, I am reminded from time to time when going over manhole covers while braking, or even the lane divider dots on the road. The brakes are basically disengaged for about 1/2 a second. It can be quite alarming if you are braking to avoid driving into the back of somebody who has suddenly decided to brake hard. The traction control can put you in similarly dangerous situations, such as when pulling out into traffic from a side road. The traction control seems to take even longer to re-engage, and totally cuts power to both front wheels.

I sincerely hope that Toyota works on these systems, if not for the current generation Prius, then for the next generation. I am considering a Toyota Camry Hybrid for a second car, and I am crossing my fingers that it does not suffer the same issues.

 

In most cases, it's probably not what you usually think of as ABS.
That "braking sag" you're feeling is regen giving up because of
heavy torque/current blips through the motors and electrics, and
falling back over to hydraulic brakes. That's not a perfectly
smooth transition. When you get wheel hop that often accompanies
said bumps under strong braking torque, the slip light tends to pop
on for an instant. But until you really start locking up wheels
with the hydraulics, it isn't ABS in the traditional sense.
.
I don't think anyone's figured out a faster way to "reset" the regen
other than waiting for a bit. Blipping the go-pedal once doesn't
seem to do it [and is usually not an option in a heavy stop anyways].
.
To compensate, get used to the fact that it happens sometimes, avoid
bumps when possible, decrease braking pressure when going over bumps
to try and not trigger it, and above all leave plenty of *space* so
you have the leeway to plan ahead and do all this. The longer and
gentler you can make regen stops, the more effective capture capacity
you get from the battery -- lower current == less Peukert effect.
.
_H*

 

<div class='quotetop'>QUOTE(alt_fuel @ Sep 30 2007, 08:52 PM) [snapback]519613[/snapback]</div>

Funny that you say that your other vehicles weren't as sensitive. I had a '94 Taurus and a '94 Grand Prix that were just as sensitive as the Prius. But they also had this nasty habit of lifting the inside rear wheel off the ground for a split second when making a right turn into a driveway apron (ramp), which would freak out the ABS mightily when it would see that tire "lock up", not realizing it was in the air anyway. In the Grand Prix you mostly just heard ABS chatter but didn't feel much; in the Taurus you almost completely lost all braking for two full seconds while the ABS tried to correct the imaginary skid. I almost wrecked the Taurus once thanks to that issue, despite having gotten so used to it that I could anticipate when it was going to happen.

Now in the Prius, as I've gotten used to it, I find that when I see the right kind of bump coming to cause the issue, I'll brake a little extra right before the bump, let off the brakes for the moment of the bump, and get right back on them on the other side. ABS won't act if you don't have your foot on the brake in the first place, and it only matters for the fraction of a second that the tire(s) skip across the irregular surface..

 

I experience the same effect since I boosted the tp to 45psi.