Downhill Assist Control (DAC) vibration

[mike508]

I have only tried it a couple of times but when using the DAC there is a vibration like it is tearing the vehicle apart. I guess it is the ABS pulsing but seems like something is loose or not operating right. I noticed the same thing once with the Hill Assist Start. I don't normally use it because of this and since it is just as easy to use the brake pedal. My warranty is about to run out so if something is wrong I want to get it fixed soon. The vehicle is a 2006 SR5 4X4. Has anyone else experienced this?

 

[Methodical]

DAC is very jerky, that's just the way it is.

it works best when in 4LO, and the shifter in 1st gear. That reduces the extra work from the engine.

You are right in that the vibration is from the ABS system/brake modulator. It sounds different than normal ABS because it is modulating each wheel independently, so four times the noise. And the amplitude (strength) of the vibration changes when two or more wheels need modulation at the same instant... so it feels very random and out of control, but it's the opposite.

The brake modulation system in our 4runners is one of it's greatest strengths.

one quick health check is this...

With the the ignition on but don't start the engine... and just start pulsing the pedal like mad. All the way up, all the way down. Fast as you can. You should get a lot of pumps before the computer yells at you as the brake assist charges back up.

I'll post back tomorrow after I tell you the number of pumps I'm able to achieve. Offhand I'm thinking like 10.

The number of pumps should be repeatable, and far more than you can conceivably need.

 

[teampwr2]

Sounds Like its working properly...What type of conditions are you using it in ???

 

[mike508]

DAC

Thanks for the input. I feel better that it in normal but fail to see the usefulness. I don't have anything else to do with my foot besides applying the brake and the ABS will activate if needed. The violent vibration can't be good for the suspension so I will pass on this feature. I'll try the test you suggested.

 

[teampwr2]

I use my DAc All the time in 4lo on extreme hill decents and it works great ...almost like cruise control for Extreme downhill angles

 

[Tariqie]

damn Nice Pic, I wish I had a hill like this

 

[Vizwar]

Re: DAC

Thanks for the input. I feel better that it in normal but fail to see the usefulness. I don't have anything else to do with my foot besides applying the brake and the ABS will activate if needed. The violent vibration can't be good for the suspension so I will pass on this feature. I'll try the test you suggested.

DAC is not something that will hurt your suspension. If you're not used to it, yes, it can be a rather odd or uncomfortable experience. It scared the hell out of the girlfriend first time she experienced it. It will save your brakes though and give you much better control of the vehicle on a steep hill. Don't give up on it just because you're not sure how it works.

 

[Kmvreter]

These features (DAC, HSA, etc...) rely on cycling the brakes to provide traction to the wheels that need them. Are your brakes in good condition?