ABS kicks in while cornering under normal conditions

What is the make/model, and tread depth of your tires?

 

do you hear the same rattling noise when you are parked and you press the brake a few times? This type of rattle is very evident when you first start your car and you step on the brakes.

 

Good point, maybe the brake actuator pump is starting to get noisy.

 

My 2006 makes this noise more often than my other Prius cars, but doesn't throw a code. I'm not sure if bleeding my brakes will make it any better, but I'm just waiting it out until I see a DTC.

 

There are no codes because the ABS thinks it's doing the RIGHT thing.
So the problem is with one of the wheel sensors. I would find a new dealership and replace the sensors.

 

Or possibly a bad strut.... But hopefully the dealer looked into that

SM-N900P ?

 

I haven't noticed a complaint similar to yours. For fun, you might check tire inflation to make sure all four tires are properly inflated.

Here is an example of the issues that would make the skid control ECU think that a wheel sensor has a problem (for example, DTC C0200, right front sensor circuit):


Speed of a malfunctioning wheel is 0 mph (0 km/h) for at least 15 sec. when vehicle speed is
6 mph (10 km/h) or more.


Speed of the slowest wheel is less than 1/7th of the 2nd slowest wheel for at least 15 sec. when
vehicle speed is 6 mph (10 km/h) or more.


Abnormal high wheel speed pulse is input for at least 15 sec.


Abnormal high wheel speed pulse is input at least 7 times when ECU is on.


Speed sensor pulse signal is instantly cut 7 times or more.


Speed sensor signal line is open for at least 0.5 sec.


The skid control ECU can also detect if foreign material is contaminating a sensor (for example, DTC C1235, foreign matter on tip of right front sensor).

Pulse waveform of speed sensor signal is abnormal for at least 5 sec. when vehicle speed is 12 mph (20
km/h) or more.

So, if a problem is going on that the skid control ECU cannot detect, it would have to be something that doesn't fit the above categories or perhaps the skid control ECU itself is starting to get flaky but its self-diagnostics haven't figured that out (DTC C1300 reports an ECU malfunction.)

By the way, there is a process that can be used to determine if there are intermittent connections between the various sensors and the skid control ECU, which is documented in the repair manual and which uses Toyota Techstream's data monitoring function.

 

I had a similar problem with a loose sensor - not Toyota, though. Essentially the gap between the sensor and the toothed wheel increased enough so that the signal dropped out at low speeds. When turning, it would be a wheel at the inside of the turn. I cleaned the seat, re-torqued the screw, and all was well. If not this problem, I would still suspect some sort of sensor issue.

 

One thing I hate about much of todays auto repair reality, is that it seems the newest generation of mechanics and technicians simply will not recognize a problem or potential problem unless a code pops up.

Trying to get a dealership repair facility to recognize a problem or a potential problem if a code hasn't popped up is like asking a dentist to put a cavity INTO a tooth. They won't do it.

I trust the owner, that has had the vehicle for 7+ years.

I ask for a inspection and evaluation of the suspension including sensors. And checking your tires is also a good idea.

I'm a little thin skinned about this issue, because (not with my Prius) in the past, I've had a very similar response given to me, the Ol...you can't have a problem because no code or indicator light has gone off...and I think that is lazy evaluation on behalf of the repair person or facility. As great and as helpful as our computer based system can be, IMO it's not perfect and not having a code, doesn't mean you don't have a problem.

The exclamation that the "Newer Models Do It Even More" is BS. I have a Gen 3 Prius, and it is NOT normal for the ABS to turn on in normal cornering.

 

No, I use 44 psi F/42 psi R.

 

A major case of "computer says No" with mechanics these days. No fault codes, no problem!
ABS sensor, shocks and tyre pressure are the obvious ones to check first

 

I'm just curious, and I don't mean to imply that it's incorrect or anything like that, … but … at those pressures do you see an even tire wear pattern?

It's just, with my tires, I don't want to run mine higher than 39F/37R as I start to see more wear in the middle of the tire when I go higher.

I know all tires are not the same, so I'm just curious.

Out of interest, what tires are you running. Mine are Goodyear Assurance Triple Max.

 

Bridgestone Ecopia EP422, even wear across the tire tread. 185/65R15 tire size.
Bridgestone Ecopia EP422

Yes, if you believe that the inside of the tread will wear faster at a higher psi then you should leave the air pressure as-is.

 

I think you have a mechanical issue. If it was any of the above mentioned you would see a DTC on the dash. If ABS engages that throws an indicator too which says ABS in a circle momentarily. And not sure what ABS kicking in sounds like as it shouldn't really make any noise when engaging. Some Gen2 had an issue with it chirping. Required replacement of the abs actuator. Expensive. You say rattling though.

If you engaged ABS you would see that ABS alert popping up on the dash momentarily. This car is very fussy about ABS operation. Everything is monitored.

You don't drive the car that much so your rotors are probably really corroded. If very corroded that tends to make the pads glazed & loud and the brakes get really grabby especially after it rains. Take a look and see through the wheel spokes how bad the rotor is. The friction brakes don't do alot of work and after 7.5 years everything's probably getting really corroded under there.
Most likely the caliper pin slider grease has dried up and things are not functioning real good in the front anymore.
Because of it's age may be time to pull the calipers off, replace the pads, cut the rotors, have the pins greased, and the fluid flushed out.

Poor caliper grease can get expensive. The caliper gets hung up and won't retract and after a few miles of that the wheel gets so hot the tire will start smoking. Alot of car fires start that way. Happened to me once on a used car I had just bought. Tire was smoking real bad but didn't catch fire.


Is the car garaged?
And has it ever been in an accident?
And do you clean the brakes as in applying pressure to them while rolling in neutral periodically?

 

Doug, if you lose the ABS you still have the conventional brakes. When the ABS failed in my 2006 I drove past the local Toyota dealer to get it fixed under warranty by my dealer. The car drove & braked normally.

My tp is at max sidewall or higher with even wear.