Any way to Test Rabs?

[Haywire6000]

So I have a 1993 with Rabs. No abs light when I turn the key on. Is there some kind of self test I can do? Also I am curios. How does the ABS work with only one speed sensor( the one in the rear end, unless there is another one I don't know about). With only one speed sensor how does the computer know when the truck is " sliding" or when the rear wheels are locked and the fronts are not?

 

[RangerNation]

That would be anti lock. Since its only detecting if the rear wheels lock up it only needs one sensor. Does the light come on ever. I would check the bulb first. I drove my 94 with the light on all the time I was to lazy to fix it.

 

[Haywire6000]

NO the light doesn't work at all. But wouldn't it need another sensor to compare vehicle speed vs wheel speed? With one sensor the computer has no way of telling of the wheels are locked in a panic stop or I'm sitting at a traffic light.

 

[Captain Ledd]

Well I tested mine on a freshly snowed road with a friend watching on the side of the road.

Of course, that's a little hard to come by this time of year in the northern hemisphere...

 

[exbass94]

NO the light doesn't work at all. But wouldn't it need another sensor to compare vehicle speed vs wheel speed? With one sensor the computer has no way of telling of the wheels are locked in a panic stop or I'm sitting at a traffic light.

The way it works with one sensor is this: If you're driving at 35 mph and you slam on the brakes, then that means the sensor was telling the computer you're traveling 35 mph and then the very next second you're traveling 0 mph. The computer knows it's physically impossible to come to a complete stop from 35 mph in a fraction of a second, so it knows you must've locked the wheels up and it engages the ABS. If you come to a gradual stop from 35 mph, the computer will see the gradual decrease in speed from the sensor, and it will know that it was a normal stop without lockup and it won't activate the ABS.