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Is there any way to know when your VTM-4 (AWD) is engaged? I know it is always 'on', but normally all the power is going to the 2 front wheels. Is there a way to know when the computer has decided to send some power to the rear wheels? I particularly thinking about hydroplaning (or ice) conditions. You might be driving along thinking you had good traction because the VTM-4 is always finding a wheel with bite. It would be good to know that conditions are slippery even when you don't feel it.

- Conrad
 

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conradsmith said:
Is there any way to know when your VTM-4 (AWD) is engaged? I know it is always 'on', but normally all the power is going to the 2 front wheels. Is there a way to know when the computer has decided to send some power to the rear wheels?
There is no indicator for VTM-4 unless you are in "VTM-4 Lock" mode in which case the light on the switch is illuminated. When it engages automatically during hard acceleration or when the front wheels slip, there is no way of knowing for sure that it's working AFAIK, unless you can sense it by the seat of your pants :)
 

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A very good idea-

Lot's of problems with folks driving 4x4s in snow- just because you can get going, doesn't mean you can stop or steer... I'd say the number of wrecks in the mountains of N.CA is half 2WD and half 4WD.

There is no indicator for the VTM4 being 'activated'. There are three outputs from the VTM4 control: differential from front to rear and then left and right rear clutches. If you'd monitor these signals, you'd see varying voltages as the torque is being manipulated/directed. Even if there was a 'master signal' that just cam on when the system was directing any torque, you'd see it blinkling all the time. Even in non-slip conditions, torque is directed to the rear wheels! to PREVENT loss of traction.

Oh well, just trust it is working i suppose...

Ard
 

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Then what is the purpose of the vtm-4 light that is on the dash...where the other lights are.....it lights up for a second when you start the car.....I'm not talking about the lock button, that has the green light when you push it in....this is a vtm-4 light in the dash. Is it like the TCS light on my TL? It lights up when there is slippage detected on the wheels??
 

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There are two VTM4 'lights', loosely termed:

A VTM4 Indicator Light on the instrument cluster
A VTM4 Lock Indicator Light on the dash at the lock button.

The indicator light on the cluster is a FAULT INDICATOR. As with virtually all fault indicators, it comes on with the initial key switch so you can be certain the bulb works.

If it comes on during use, it is due to several factors: internal fault code in the VTM4 computer, over temperature in the differential, electrical interference.

It is NOT a TCS-type indicator.

If it DOES come on during use, it will stay on until reset (by turning the car off and restarting). If the fault is still there it will come on again.

At least that's my understanding from the service manual.

ard
 
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