We've had this issue for a while and though (hoped) the recall on the ABS unit would fix the issue. It did not.
The ABS light is on and after having the reall done it is stilll there. The dealer thinks it is probably a wheel speed sensor. I've searched but have come up empty handed on how to check these sensors. Does anybody have infomation on this?

Thanks in advance!

 

From my limited knowledge of the ABS, if it were a wheel sensor, then the tire pressure warning light would likely be lit up also. The ABS uses 'tone rings' to sense the rotation of the tires. The tone rings are toothed rings that pass by a sensor that gets a frequency and passes that square wave to the computer. If the frequency on a given wheel is different from the frequency on another, either you are turning or you have two different diameter tires mounted.
The same signal is used by the ABS to determine of one wheel has locked up while the others are continuing to turn. The only way that can happen{I think} is for one wheel to be skidding, or the vehicle has to be in two parts, one going down the road, and the other sitting still.
So, I agree that the dealer should check your tone rings and pickup coils. If one of the pickup wires has been damaged that will also cause the ABS problem light to be lit. The ABS light might have 'priority' over the tire pressure warning given they use the same sensors. I know Nissan uses pressure sensors that are mounted in the inside of the tire{$$$$}, attached to the valve stem. I *think* Ford uses the method I described as you have to 'set' the sensor when you have just checked tire pressures all around.
tom

 

In the current manuals, all four wheels should read within 2mph of eachother IIRC.

A auto mechanic said by connecting a DMM reading AC volts, spinning a wheel by hand and comparing to the other wheel a bad sensor could be detected. The sensors are just prox switches which generate pulses but spinning by hand seems a bit iffy to me.

 

Tires are all new (same size) and I do not have TPMS (so this isn't and issue) so I will be looking for the connectors for all 4 sensors and hooking up the meter to them. If not it's off the the mechanic- or maybe just live without ABS...

Thanks for the inputs guys!