ABS Malfunctioning Offroad?

ElectroBoy said:

I’m wondering about this too. A few weeks ago someone pulled a bone-headed maneuver cutting across my lane at 45 mph and slowing down. I jammed on the brakes and really needed to lock the wheels up hard. But the ABS kicked in and gently pulsed the brakes with a squishy feel to the brake pedal. I would have hit the guy but since he was traversing across my path right to left he got out of my way just in time. It really felt wrong how the ABS responded like that.

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RonJR said:

I don't think this behavior is normal - I sure haven't experienced anything like it. I'm wondering if your brake booster is failing. A normal stop, using steady pressure on the pedal, doesn't require a lot of capacity from the booster, and it can maintain pressure easily. On the other hand, when the ABS is pulsing, the booster has to continually build up pressure between pulses. If it is weak, you could run out of boost pressure and be left with no power assist. That would feel like your brakes were "locked out", because without power assist, disk brakes are pretty ineffective.

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Jazz30-06 said:

Also, the brakes work fine anytime the ABS isn't kicking in.

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RonJR said:

That's my point. A single push of the pedal is easy for the booster to keep up with. In fact, you typically get power assist for a couple of pedal pushes even after the engine dies. But when the ABS is active, it's like pumping the pedal 5 times or so per second. Much harder for the booster to keep up with.

An experiment you could run is to find a quiet country road with no traffic, accelerate to a moderate speed, and then do a high performance stop by pumping the brakes as rapidly as you can. See if the brakes appear to "fade" or if you get any perceptible change in stopping power as you do that.

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Ray Dunakin said:

The problem is that the ABS is intended to prevent skids, not stop you quickly. So if you're on loose dirt, gravel, or snow, it actually makes it more difficult to stop fast. In those conditions you want the brakes to lock and the tires to dig in, and the ABS won't let them.

It drives me nuts when I'm off-road or on a dirt/gravel road. I wish there was a way to shut it off when I'm not on pavement.

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Mantilgh said:

I’d say just put a disable switch in.

Is ATRAC that great?

And do you use it?

Did you use it in your first situation in your first post?

If you did, did it help?

What mode were you in when you were spinning?

Sorry. Not try to be a D, just curious.

Sent from my iPhone using Tapatalk

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Jazz30-06 said:

Does anyone know what is happening, if this is normal, and/or if there is a way to disable ABS without losing ATRAC?

Thanks,
Zak

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Pathfinder5243 said:

Are you in 4lo with the center locked when this happens?

Are you running street tires or AT's?

Have you done the ABS recall which keeps you from power braking?

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RonJR said:

That's my point. A single push of the pedal is easy for the booster to keep up with. In fact, you typically get power assist for a couple of pedal pushes even after the engine dies. But when the ABS is active, it's like pumping the pedal 5 times or so per second. Much harder for the booster to keep up with.

An experiment you could run is to find a quiet country road with no traffic, accelerate to a moderate speed, and then do a high performance stop by pumping the brakes as rapidly as you can. See if the brakes appear to "fade" or if you get any perceptible change in stopping power as you do that.

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Jazz30-06 said:

2H or 4H unlocked

Defender LTXs

What recall? I have my VIN registered on Toyota's owner site, but it shows no recalls active for my VIN.

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Pathfinder5243 said:

Depending on the pressure you're running in the tires and that they're street tires will make you slide more off road. I have similar issues with the VCS turned on. Make sure it's off and you shouldn't have this issue.

If you don't have an open recall then it's already been done. They updated the software to kill power if the brake is applied. Keeping you from being able to use them at the same time.

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Jazz30-06 said:

...
The first was that when I had tires spinning in snow and tried to brake them to avoid creating ice, the ABS kicked in and wouldn't let me use the brakes. So, the tires just kept spinning and created the ice anyways. I justified this one as "tires are all spinning at a different rate, so OK, I guess".

The second was actually at very low speeds in uneven terrain. I was parking behind someone and when I tried to stop (at like 2 mph) the ABS kicked in again and locked me out of my brakes. I almost hit the guy because of this and it greatly concerns me that this is an issue if I ever find myself on a hill and this system kicks in.

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techno said:

In your first example, I'm wondering if traction control activated at the same time you applied the brakes, purely coincidentally. As you know, atrac is ABS based and only kicks in when the wheel(s) start spinning. Perhaps your brain and the 4runner brain came to the same conclusion simultaneously?

In your second example, it sounds similar to something I experienced last year, but I was driving at about 40mph instead. In my case, a wheel speed sensor (elcheapo ebay one) failed and was sending false readings to the computer. With abs kicking in and me trying brake, I got pretty much no braking at all. After it happenned a few times, the check engine light came on with ABS error codes. If you have the same thing happen again and you have access to a code reader that read ABS codes, it would be worth looking for a pending code.

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Jazz30-06 said:

2H or 4H unlocked

Defender LTXs

What recall? I have my VIN registered on Toyota's owner site, but it shows no recalls active for my VIN.

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