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DAC flash with clicking noise while starting uphill

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Old 12-12-2012, 10:05 PM   #1
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DAC flash with clicking noise while starting uphill

Hey guys, new to 4x4 and Tacoma's. purchased 2012 Baja Ed. After parking on a step uphill I tried to drive and noticed something strange. With the let off of the brake and pressing on the gas my truck slipped while rolling backwards. The DAC flashed form the left side of the dash and I noticed a clicking noise until I gave enough gas to go forward.

I thought Imay need to use the DAC so I put the truck in neutral and pushed the DAC button after putting in 4X4. It turned on (flashed on right side, not left) of dash. however I still experienced the slip. This can't be normal. Do I have a problem or am I just doing something wrong.

I have read the manual but I'm still a little confused with all these off road features. Any info is appreciated.

Karl
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Old 12-13-2012, 05:41 AM   #2
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That's normal. The first thing you heard was the "Hill Start Assist". It applies the brakes to keep you from rolling backwards. It works automatically in 2 and 4 wheel drive.
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Old 12-13-2012, 08:45 AM   #3
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Ok not at work anymore, I can answer more in depth.

Like I posted before the clicking and flashing light is normal for the hill start assist. The light just flashes to let you know it's active. Its used for those times when you're stoped on a hill and as soon as you let off the brake the truck wants to roll backwards. Well this keeps ya from doing that. The DAC on the other hand does not work automaticly, IIRC the DAC or Down hill Assist Control only works in 4 low. This completely controls the brakes for you while easing down a steep decent giving you more control in steering and so on. DAC will disengage automatically as soon as you hit the brake ( be careful doing that while going down a steep hill, I learned it ain't fun lol)

Now as far as the other 4 wheel drive modes...... good luck. I'm still learning mine. I can tell you this much about though. 4 Hi will do most any 4x4 task you try, if you need for torque or traction 4 Low WITH ATrac and the rear diff locked is where it's at. The rear diff only works in 4 Low too. ATrac acts like a locker to send power to the wheel that's got traction. From what I have seen of it, its pretty bad ass and you will like it. There are multiple threads on this site that discuss the different drive modes for our trucks, look one of em up and see what you can get out of em, I tried and I'm still left wondering about some stuff.

Welcome to Tacoma World, feel free to stick around and ask more questions, most guys are cool here and are more than willing to help out.
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Old 12-13-2012, 08:51 AM   #4
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Like MudFlap said it's Hill Assist Control. There is no manually turning it on or off. It's on in gear. It will hold your truck in place while you switch your foot to the throttle. It deactivates after a certain amount of time. Could have been your problem.

Also, to use Downhill Assist Controll, you must be in 4 Low and in the gear of the direction you are going downhill (forward or reverse) for DAC to turn on.
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Old 12-13-2012, 08:54 AM   #5
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In vehicles equipped with both HAC and DAC systems, an active wheel speed sensor is located in each wheel. The sensor uses a rotating magnetic encoder located in the wheel hub to detect a magnetic field. Once detected, it delivers digital signals based on the change of magnetic poles. The detection of the magnetic fields allows the use of magneto-resistive (MR) effects. The active wheel speed sensor is then able to measure the vehicle's extra low speed and rotating wheel direction.

Extra low speed detection is possible because the output signal of the active wheel sensor is proportional to the amplitude of a magnetic field. Because the magnetic field encoder does not depend upon the basic wheel rotation speed, the active wheel sensor can deliver a precise signal, even if the wheel speed is extra low.

The active wheel sensors detect rotation direction through the use of two MR elements. If the magnetic encoder detects a change in rotation, the phase between the two MR elements are shifted upside-down. This allows the active wheel sensors to digitally process the signals and provide wheel direction information. The sensor output is provided in three levels of current via a two-wired interface. In the case of a forward movement, the output is a two-level pulse signal. A three-level output pulse signal is provided in the event of backward movement.

The basic function of the HAC system is to help increase control on steep upgrades and stopping and starting on slippery surfaces. The HAC system is designed to help prevent the vehicle from rolling backward or slipping sideways during transition from a stopped position to climbing an upgrade. The system is automatically activated when the transmission is in any forward gear. The HAC system controls the brakes to help stop the individual wheel or wheels, which helps prevent the vehicle from rolling backward or slipping sideways.

The HAC system determines the driver's intended vehicle direction from the present gearshift position of the transmission, the moving direction of the vehicle wheels, and the wheel speed of the four wheels through the use of active wheel sensors. When backward rolling or slippage occurs, the HAC system is automatically activated. Upon activation the HAC system gently applies the brakes. The HAC system measures the necessary brake pressure of each wheel to help prevent individual wheels from locking and causing vehicle slippage.

The DAC system assists engine braking to improve directional control during descent on steep or slippery surfaces. When in 4WD low range and with DAC activated, if any one wheel accelerates beyond or below a two-to-four MPH low-speed setting, the DAC system will control the brakes to help ensure the vehicle continues in a straight position when going down a hill. The DAC system is automatically de-activated if the driver depresses the brake pedal, accelerator pedal, or the DAC button.

The active wheel speed sensors enable the operation of the DAC system by determining current road conditions. The system designed to determine current driver operation through an accelerator pedal angle sensor, master cylinder pressure sensor, and the setting of the L4 position switch. DAC next determines its target vehicle speed of two-to-four MPH based on road surface and vehicle driving conditions. When the vehicle accelerates during descent, allowing the vehicle speed to exceed the predetermined speed, DAC is activated. The DAC system will calculate the required brake hydraulic pressure for each wheel, allowing each individual wheel to meet the target vehicle speed.
Hopefully this helps.
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Old 12-13-2012, 10:07 AM   #6
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I thought the hill assist was only in manual tranny's... I'm going to have to look into this some more I guess.



EDIT: huh... Apparently HAC and DAC are only available on automatics. At least for the 2013's. I have DAC but I am pretty sure I don't have HAC.

Hey GP3 does your 2007 have HAC?
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Old 12-13-2012, 10:41 AM   #7
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Quote:
Originally Posted by BradyT88 View Post
I thought the hill assist was only in manual tranny's... I'm going to have to look into this some more I guess.



EDIT: huh... Apparently HAC and DAC are only available on automatics. At least for the 2013's. I have DAC but I am pretty sure I don't have HAC.

Hey GP3 does your 2007 have HAC?
Automatics only.

Yes, my 2007 has it. VSC/TRAC/HAC/DAC/AUTOLSD/ATRAC was optional package on the TRD Off Road for 2005-2008.

If you have DAC on your 2005, you have HAC.
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Old 12-13-2012, 11:34 AM   #8
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Quote:
Originally Posted by GP3 View Post
Automatics only.

Yes, my 2007 has it. VSC/TRAC/HAC/DAC/AUTOLSD/ATRAC was optional package on the TRD Off Road for 2005-2008.

If you have DAC on your 2005, you have HAC.
I see. Interesting. So how would I test this? Go to a steep hill and put it in gear and let off the brake and see if it rolls backwards?
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Old 12-13-2012, 01:05 PM   #9
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Quote:
Originally Posted by BradyT88 View Post
I see. Interesting. So how would I test this? Go to a steep hill and put it in gear and let off the brake and see if it rolls backwards?
Yep.

It will make noise while the brakes do it's thing, and if I remember correctly, the slip indicator (truck with skidmarks) will light up while it makes noise and does it's thing. Careful though, it will deactivate after a few seconds.
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