02 Ranger ABS problem

ABS works by looking at the individual tires, and if any tire stops spinning
while the others remain in rotation, then the tire that has stopped will get
its braking force reduced so that it can resume rotating. The brake pedal
will pulsate very quickly when this happens. The braking system will also
make a noise corresponding to the pulsating of the pedal.

You disconnected a sensor, this disabled the entire ABS system, and lead you
to perhaps replace the wrong component. What you did was to deliberately
break the system as a troubleshooting technique. I think the technique is
sound, but the results were misread.

When the system detects NO INPUT from one or more sensors, it will shut
itself down because it cannot control skidding without input from every
sensor in the system. If your brake system is pulsating, and the pulsating
comes from the ABS system, then the system is detecting that one or more
tires have locked up while the others remain turning. Normally this behavior
is associated with aggressive application of the brakes.

There are 3- and 4-channel ABS systems. A 3-channel system looks at the two
rear tires in tandem, and if either of them begin to skid, the braking
pressure to both rear tires is reduced to stop the skid. The idea is that a
rolling tire offers more directiional stability than a skidding one,
although a rolling tire may also take longer to come to a stop. Increased
stopping distance with driver control is sometimes a better option than an
out-of-control skid. The whole stopping distance being longer or shorter is
a matter of great debate, but directional stability is generally preffered
at any cost. So, if the stopping distance is both shorter and has more
control, then there are two benefits of ABS, but if there is increased
control at the cost of greater distance, then ABS offers one benefit. Either
way, having ABS is generally viewed as being better than not having it.
Trucks and vans are more likely to have 3-channel systems than passenger
cars, and 4-channel systems are better than 3-channel.








"gntry" <gntry.RemoveThis@verizon.net> wrote in message
news:qYsWh.4292$bZ2.1656@trndny01...
> 2002 ford Ranger 4x4. front wheels pulse at slow speeds when brakes
> applied. I thought it was the front ABS speed sensor. Disconnected
> passenger side and problem goes away. Replaced sensor (costly replacement
> $170 bucks) plugged in and problem returns. What else could it be?
>
>