4Runner Auto Braking For No Reason

So this is a problem I’ve been fighting for almost a year now. I’ll start off with saying I’ve replaced my speed sensors, yaw sensor, and I’ve done multiple zero point calibrations.

Sometimes when I am driving either on hills or even on flat ground, my slip light comes on and the brakes just lock up without me even pressing the brake pedal. No beeping or TCS light. Just the slip light flashing. Every time that happens it goes into limp mode and I have to pull over, restart the vehicle, then it works fine again. It usually does it after I am parked uphill or downhill. But can still happen even after I am parked on flat ground.

I do have a leveling kit on it. I was told to level out the yaw sensor to make up for the tilt but that didn’t work. Every time I have replaced a sensor or tilted the yaw sensor I done a zero point calibration. Like a real one with a snap on scanner. I’ve also checked codes after restarting and without restarting and I get nothing.

I’m tired of dealing with this and I would like to just sell the vehicle but I don’t want to do that since it could be pretty dangerous sometimes. I don’t really know what to try next. Some help would be amazing, thanks!

 

It seems you may have to see live data when driving. It would have to be at the VSC level.

 

Thanks! I’ll have to try and figure that out. I can maybe get it to activate after parked on a hill again cause it seems like it consistent with that. I use a coworker’s scanner so I can see if he knows how to pull up live data on it.

 

Turn off the braking feature and it will still scream at you, but I would start there!

Steve

 

Sounds good. I’ve tried turning off stability and traction control while it was happening but that didn’t change anything. Maybe the live data will show something different

 

On other vehicles, ABS/VSC can intermittently activate if one of the wheel speed readings drops out momentarily, like a broken tone ring on the wheel bearing or debris/rust flake stuck to the tone ring. If you can see wheel speed as live data with your scan tool, you can jack up the vehicle and spin each tire by hand, while checking for signal dropout.

 

What year is your vehicle?

 

2012

 

Thank you, I will try this

 

Do you know if the 2012 4Runner is the tone ring on the cv axle or on the wheel bearing.

 

^
It's a magnetic strip on the inboard side of the wheel bearing. If you see signal dropout in the data, you'll need to remove the wheel bearing from the knuckle to inspect. Same design 2003-2024.

 

Okay thank you. I got time on Saturday to look at it and I will let you know.