Brake Pedal Issues

I just bought a 2020 4runner TRD in July. No modifications and barely hitting 5K miles.

Over the last week, the brake pedal has failed 3 times. All times have been around 30-40 MPH, no cars in front of me. As I slowly press the brake down it randomly seemed to depress lose pressure and end up all the on the floor while not stopping. As I release the brake and the press again, it seems to work again.

I figured it could be a master cylinder or abs issue, but the dealer is saying they looked it over and nothing is wrong. They scanned the car and it showed the emergency brake system setting off at those three exact times. The service advisor said if the emergency braking system was activated it could be why the brake pedal went to the floor. That makes no sense to me. Under no circumstances should the pedal go completely to the floor. In addition, typically when the emergency braking goes off, lights and alarms go off in the car. None of that happened. There was also no reason for the car to emergency brake.

Any suggestions? The dealer wants me to pick it up but frankly I'm not comfortable driving it.

(edited for some clarification)

 

I'd be inclined to try another dealer. Brakes are kinda important! As for losing pressure by applying the emergency brake, I have trouble believing that. I'm new to Toyota's and 4Runners, but emergency brakes are generally mechanically linked to the brakes so they still work even if you lose fluid.

Any chance you used the emergency brake to stop when the service brake didn't respond? That'd explain what they saw on the computer. If you didn't use the emergency brake, what did you do to stop... Maybe pump the pedal?

Did they check the fluid level?
Did they check the lines for air?
Did they inspect the pedal to make sure nothing was physically messed up there?
Would they be willing to stand in front of it while you accelerate towards them and brake at the last minute?

 

what was your last vehicle and are you familiar with ABS activation and what it feels like?

(Not being sarcastic, serious question)

 

I am familiar with ABS. From my experience ABS can cause the pedal to drop a little and pulsate. None of that happened. Pedal just loosely went to the floor and no stopping. No reason for ABS to go off in the 3 situations either.

 

Sorry, to clarify it was the emergency braking system getting set off (pre-sense I think they call it?), not the actually emergency brake. What is odd is that when that system goes off there is normally lights and warning sounds which there were not any of. I told them I am not picking it up and to keep looking, so I am waiting to see what else they have physically looked at other than just scanning the car for codes. I checked the fluid level after it initially happened and fluid was full and didn't see any leaks under the car.

 

I wonder if the loss of pressure at the foot is the pre-sense applying the brakes therefore there would be a change in pressure at the brake pedal because technically the brakes are already activated? When this happened did the truck slow down at all on its own or was there any indication the pre-sense system was being activated? I agree, if a code of the braking system coincides with these incidents than something is wrong. If I know anything about Toyota is that they take braking and acceleration pretty seriously now. Ask them if they would write you a letter stating that there is no fault in the braking system that you could show your insurance company if you rear-ended someone or worse, ran someone down crossing the road. I like this "Would they be willing to stand in front of it while you accelerate towards them and brake at the last minute?" the ultimate test of "how sure are you?

 

That was the first thought, but the pedal went completely to the floor as if no brake fluid in the car and the car did not slow down whatsoever. There was no indication of the pre-sense system being active either. No light, alarms are anything. A letter is a good idea.

 

You might want to also ask them why the pre-sense was activated but you have never seen any indication it was, no lights, alarms, sounds, etc yet it is throwing codes that it did activate.

 

Since this seems to be an issue for other people in the forums, I thought I would update everyone in hopes it helps someone. I ended up escalating my issue with Toyota Corporate because the dealer could not find anything wrong and wanted to send the car home. They apparently sent a field tech and were able to duplicate the issue but can not pin point the cause. They will be replacing the entire brake system on the car and I was told will be sending the part to Japan to investigate since it is a major safety issue.

 

Well that is good news! I wonder what replacing the braking system means. Does it mean the master cylinder or something else? I guess in my mind as I was reading that is that the would rip out all of the brake lines, callipers, cylinder and any other parts related to the braking system which obviously isn't really logical. If they can't pin-point what is failing how do they know what to replace?

 

My guess is that they are just replacing every part that could possibly cause this issue. They mentioned replacing the master cylinder, abs control module and abs brake actuator among other things. My best guess is it has something to do with the ABS. My concern is that who's to say the new parts don't have the same issue if they don't know the cause and it seems there are other vehicles with the same problem.

 

I don't see this specifically mentioned, but what is the likelihood that this problem is possibly related to an issue with the TSS?

If a malfunction in the TSS is the cause of a disappearing brake pedal and loss of braking, Toyota has a huge problem on its hands. Remember the "unintended acceleration" fiasco?

Hopefully this is a one-off occurrence. PITA for the OP, though. Good luck with the fix.

 

Scary. My bet is that it has something to do with these stupid pre-collision systems. Thanks, Toyota.. put a bunch of crap on my truck so that idiots will pay LESS attention while driving, just so that they can fail and send my paying-attention-ass into the ditch or car in front. I'm rolling my eyes as hard as I can right now...

I fear for the future of driving. Seems like every time I drive my new truck, one of these damn systems is triggering a new light on my dash that I have to go look up out of fear of something being broken. Nope, it's always just a little dirt, ice, or maybe the damn thing is just moody that day...

 

Yesterday the breaks on my 2020 4Runner TRD complete failed… almost killed me and my passengers.. took to dealer on peri ious oil change and told them breaks act funny and to check my pads… they said it’s fine… now this… had it towed there and dealer says $1500 to change the rotor and pads and it’s normal for 38killometer car for that to happen….. absolute BS (jimmy Paterson Toyota in Vancouver Canada)

 

Thats messed up! Sounds like a classic case of extortion.

 

Glad you are getting some resolution. From your description, it definitely sounds like there is/was a serious malfunction.

I have see a few other posts in the past with a similar problem as yours.

From my understanding the ABS uses a self contained high pressure pump rather than a traditional brake booster which ran on intake vacuum. I have read that a replacement ABS system is terribly expensive.

 

Holy Schnikey! This is some scary stuff! Good reminder to keep one’s emergency/parking brake in good working order and well adjusted.

My emergency brake got fairly loose after the first few thousand miles. Figure it was a bit of cable stretch. I’ve adjusted it twive over the last 20,000miles and finally seems to stay in adjustment to where it will hold the vehicle on securely. These modern drum in disc designs suck compared to drums of the past, but It’s better than nothing if you have a major brake system failure.

@kourosh , what the dealer fed you is complete BS. Losing your entire braking system every 40,000 km as a normal thing is the stupidest most dishonest thing to say. I’d be pretty pissed off if someone said that to my face.

 

I'm torn on this one. Kind of damned if you do or damned if you don't. If you don't use your e-brake all the time on a drum in hat system like the 4Runner then the drum face for the e-brake shoes rusts and doesn't provide a good contact surface no matter the adjustment. Yet the ratchet style caliper like on my Caravan just never seems to fully release and always seems to drag just a bit. And yah the Dodge eats brakes. With salty winters just aggravating both styles of e-brakes. I'm applying the e-brake in my 4Runner while in motion every few weeks just to keep the rust down and things loose. Even though the 4runner loudly protests.

 

Ive never had a problem with rust that I know of. I always use my e brake. But now that you mention it, i never use use it to stop…just to hold. I think ill start using a bit in motion to bed them in.

drum brakes of the past would bed in automatically since they were used hydraulically for regular braking…so you bring up a really good point.