5th Gen Anti-lock Braking Issue on Ice and snow

I just had a bad experience with my 2021 4Runner Nightshade. Driving in Snow and Ice conditions the other day and it seemed like the anti-lock braking system was not working at all. At slow to very slow speeds on the snow and icy roads, the truck just slid when I tried to stop. Never pulsed the pedal or heard any clicking sounds, or other indication that it was working.
The truck has 40K miles on it.

Anyone experienced something similar in the ice and snow with late model 4Runners?

Also, during this drive, the truck got snow and ice all over the front end, causing parking assist alarms, and caused the crash detection system to act up, by alarming when not close to another car, and also switching off when the sensor got iced over.

Thanks,
Dan

 

Is it possible that you hit ice without snow tires and all your 4 wheels had 0 traction? For anti-lock to work, the car needs to know it still moving. It does so by looking at each wheel speed sensor. If none of the wheels are moving at all, the car would think it already stopped.

You have to old-school pump brakes. Also snow tires are a very good idea.

 

Thanks for the feedback Sin4r.
By the feel of the truck, I expect all four wheels were sliding at the same time in this case. I'll ask the obvious question here, isn't that the primary purpose of the anti-lock braking system, to prevent lock up of all four wheels and loss of control?

I tried to pump the breaks in one case, and it did nothing.
I spoke to one of the more experienced service advisors at the local Toyota dealer.
He said his Tundra did the same thing and gave me a similar explanation about all four tires locking/sliding and thus, the system not knowing its moving.

I own a 2009 G8 GT that also has anti-lock braking system, and it works to prevent lock up of all four wheels.
I've had similar happen in the ice/snow and it worked as expected, releasing/pulsing the brakes to save me.

Would like to get input from Toyota on this one.

thanks,
Dan

 

If the truck is already sliding and the wheels aren't rolling, the brakes are not in a locked condition. There's nothing an anti-lock system can do to bring them out of a condition that they aren't in. It also wouldn't help for it to just apply the brakes regardless of its normal logic, because if they are sliding instead of rotating, your truck will continue to just slide merrily along until it reaches something that isn't ice.

 

In ABS system design there's a parameter called slip ratio, which is the % of lockup and slip that gives the shortest stopping distance. The optimal slip ratio isn't 0%.
Remember ABS isn't magic. If you're on ice with shitty 20" all-season tires the stock Nightshade comes with, what you experienced was the best stopping distance your 5000-pound SUV could manage.

You can improve braking performance on ice by putting the transfer case in 4hi. On AWD models you'd want to lock the center diff.

 

Really? That's a new one. Please explain this logic. Not trying to be a smart-ass, but I've driven 4WD vehicles on snow and ice all of my life, and this is something I've never heard, nor experienced.

 

Practice somewhere (preferably open level ground) by applying a tiny touch of gas while gently depressing the brake pedal. This will allow the rear wheels to rotate and the anti-lock braking system to be able to detect the front tires have stalled out. This technique mimics the ATRAC system in my truck (which I've tested out on my last outing.) See if this works for you if you don't have ATRAC in your T4R so the next time it happens you'll have something to try in order to regain control.

 

Due to weight transfer, normally the front wheels provide 70-80% of the braking grip. Putting it in 4WD allows the rear wheels to contribute more braking grip due to the locked driveline. 14% better stopping in 4WD vs. 2WD in the Tacoma:



Since you have a Limited, you can experiment with this in an icy road or parking lot and compare braking performance with a stopwatch between center diff open and center diff locked. In AWD crossovers (Jeep Compass, Hyundai Santa Fe) I also notice a marked improvement in stability in turns on snow and ice with the center diff locked.

 

If all four wheels are locked up how will abs be able to tell a difference between that and being stopped? abs only works if there is traction and it sounds like you had zero traction. I would suggest you invest in better tires for the condition and/or don't just keep the pedal mashed all the way to the floor.

 

I highly recommend improving tires. It is rarely, if ever, I experienced 4-wheel slide on ice in any car that had snow tires equipped. Traction control is powerful safety enhancement feature, but it requires good tires to work optimally.

 

Since the purpose of ABS is to maintain some control when braking, I’m wondering if the computer decided that locking was the way to go to stop the vehicle when moving at such low speed and without steering input.

 

Gents,
Appreciate the comments. So, the 4Runners have no other means to discern if all four wheels are sliding/skidding?
That is still puzzling to me, when considering the reason for antilock braking systems. For example, if you're driving on the highway and it's raining, and there is an emergency braking requirement, all four wheels lock and you start skidding, and the anti-lock braking system does not work because all four wheels are locked.

During this drive in the ice and snow, the truck would slide almost every time I applied the brakes, and I was easing into applying the brakes, and letting off as it started sliding and easing into them again and it would slide to a stop. I was going slow, and it was behaving differently than it did at previous times on ice and snow, so the only difference I can figure would be the tires. I still have some decent tread left on them, like 5-6mm. I even tried once to turn the wheel a little bit while braking, and it just kept sliding.

I will try locking the center diff/using H4L in the next opportunity, but its March in St. Louis and we may not see any more ice or snow this year.
New AT or MT tires will be installed before next winter.

thx.

 

They have wheel speed sensors. Unless those are damaged, it knows whether the wheels are turning.

That is not what I would expect. If the wheels are locked, the ABS will release them for short intervals as expected, assuming they detect the wheels turning during those intervals.

If I recall, in the ice scenario, you said you applied the brakes after a 4-wheel slide had started. In that case, the some or all wheels may not have been turning at all. In that instance, neither locking up the brakes nor releasing locked brakes is going to decrease stopping distance until some tires are on a surface with enough traction for them to turn. In the rainy highway example there's nearly always enough traction to turn some of the tires on wet pavement.

 

If the driveline/wheels are not spinning, how do you expect the car to know it is moving? You need to give it something to work with

 

This is not the way to properly use ABS brakes - just FYI. ABS brakes by design "pump the brakes" as a system (that's a laymans way to put it). To properly use ABS, you should hit the brakes and keep steady pressure on the pedal and the system will do it's thing. I suggest taking a defensive driving course to learn how to properly use the systems as designed for emergency use.

 

I've had better luck pumping the brakes vs. steady pressure on snow and ice. Despite being the "wrong" way to use them.

It may be like gravel, where locking up and digging in will actually stop you faster than keeping the wheels turning. It takes so little to lock up, essentially the ABS has you doing zero braking instead.

 

I’ve had the abs cycling the brakes at slow speed (1 to 2mph) and refuse to stop, which was annoying because sliding would have been a quicker stop.

The weird behavior (either activating or not activating abs at very slow speeds) seems to be dependent on various factors baked into the logic of the system. Which don’t seem easily predictable to me.

I like the reminder that 4wd (w center diff locked) can actually reduce stopping distance and help
Modulating them at the threshhold. Need to remember that next time.

 

I ran into this twice today. Once on a downhill at a stop sign on gravel, and then when coming home. At both times I was moving pretty slowly anyways (because of conditions), and applied the brakes (not agresssively) and the car basically slid to a stop. Very minimal feel of ABS.

 

I tried this on my 2011 going down slight slope, 5mph or less and hit the brakes hard. Slid for a fraction of second then the ABS kicked in-pulsing. I have also been going 2-3mph hit the brakes, slid slightly with no abs activating. Is the abs brake pedal pressure dependent?

 

Not Toyota specific, but i can also find information on intenet that ABS is only active above 6km/h.
I have not tried this on my 4runner yet. I will have the opportunity to do so in the next two days when there is supposed to be a lot of snow here.

 

Turn your Trac and Skid Control off. While stationary, push and hold Trac button and dash lights will come on. I had same problem in my Limited being squirrelly until I turned Trac off. Drove like a 4wd then. I'm not interested in gadgets

 

Was in PA last week, snow and ice on Cresson Mountain, US 22.

AT tires were useless. Scary.

I was skatin' like Tonya Harding...

 

Even the highly rated Blizzaks can do poorly on ice. Fresh studs are the only thing that works on ice and you still have to be careful.

 

This sounds EXACTLY like what I am experiencing in my 2021 4Runner in snow/ice: the brakes lock up, the brake pedal goes rigid, there's a grinding/thumping noise (from the brakes, presumably), the slippery road light comes on, and the car DOES NOT STOP. This is a dangerous malfunction IMO. I took it to the dealer and more or less they shrugged their shoulders, saying the car was behaving within factory specs even though the car would do this predictably in their parking lot. Turning the Trac/skid stuff off helps only slightly, but annoyingly, I keep having to turn this off because it keeps coming back on automatically. You don't have to hit the brakes that hard for this condition to happen. I'd rather risk getting stuck in snow driving our 2-wheel drive car than risk being unable to stop. I appreciate that the tires can make a difference, but the brakes should not be behaving this way, regardless of which tires are on. I've been driving in snow/ice/jeep trails for 30 years and the only time I've ever experienced something like this was in a car with malfunctioning brakes. This really makes me reconsider purchasing this car.

 

When there is minimal to no traction to be had, the anti-lock brakes pulse the brakes rapidly to keep the wheels turning slowly and allow the vehicle to (ideally) still turn when braking as opposed to locking the wheels and losing steering.

(and also to keep the vehicle from spinning out when hard braking with one side of the vehicle on a very different surface than the other)

It does not reduce braking distance.

What previous vehicles do you have experience with? Is this your first ABS-equipped vehicle?

If it’s seriously underperforming compared to what you’re used to, perhaps it’s a tire issue or something is different?

 

I can't quite imagine that your 4Runners are so bad or don't work properly?
I am now driving my 4 Runner for the second winter and have been able to test the handling on ice and snow sufficiently (with Blizzak DM V3). For me, the ABS and stability control do exactly what they are supposed to do.
Yes, there are situations where you can't stop. But that doesn't surprise me considering the weight of the toyota and the wide tires. When going downhill on slippery surfaces, sometimes I've also had to let go the brakes and look for a more grippy surface on the side of the road. But this hasn't just happened since driving the Toyota.
Especially the first winter, when the Blizzaks where new, the grip surprised me a few times. For me, it's one of the best winter cars I've ever had. In my experience of almost 30 years of winter driving, the tires are the most important thing (are the only connection the car has to ice/snow). A set of winter tires is good for driving a second winter, but mostly not for a third winter. More important than the tread is the aging of the rubber. (I ride a different tire set in the summer)

 

The 4runner does truly act funny at very slow speeds (1 to 3 mph?) in some very specific very cold/glare ice situations. The abs just refuses to transmit any hyd pressure to the brakes and it just rolls. The problem is that if the 4runners abs programming simply allowed the tires to lock and skid over the ice at those slow speeds, it would stop almost immediately.

 

Gotcha, I'm wondering if a switch to the fuse would help then. (Wondering if there's any difference in 4Lo too.)

 

Nothing but studded tires will help in ice. With no/low friction at slow speeds there is no feedback to the ABS system to do anything. ABS is also not meant to stop you, its meant to help keep the wheels rolling while applying just enough pressure to slow without locking up for added control, but with no feedback they will just lock up as if you are stopped.

 

I doubt I was in 4lo the few times I experienced this. But I think 4lo turns off abs, so it probably would have let me lock the tires and stop.

Deactivating abs wouldn’t be worth it though, because it works as intended in other snowy/icy situations It’s only a problem in very specific icy/slow speed conditions.

I think most other cars I’ve had just deactivate abs at these nearly stopped speeds, and let the tires skid to a stop naturally. Instead,
the 4runner just keeps steamrolling in…in fact, as a driver it feels exactly like this: