I have a 2005 F150 FX4 with about 19000 miles. The ABS light has come on 3 times in the last 10,000 miles. All three times it was the rear speed sensor. I noticed it first happened AFTER i had installed 33 inch tires on a 2100 mile trip the light came on after about 1500 miles and stayed on until the truck was shut off and turned on again. Took it to the dealer and they changed out the rear speed sensor. The second time it happened on a 1500 mile trip about 900 miles into the trip the light came on again. Took to the dealer and it was the rear speed sensor. Believing that it was due to the larger tire diameter I purchased a tuner to program the correct tire size. I drove for about 4000 miles with no problems and then on a 1900 mile trip the light came on again. There was no snow or water, the tires did not spin. On ALL ocassions I was towing another vehicle when it happened. This time the dealer checked the "exciter ring" in the differential and replaced the rear sensor and said everything was fine. Does anyone have any ideas as to what could be the cause? or is anyone having similar problems that have been corrected?? Thanks

 

The exiter ring you are talking about is a geared looking thing with square teeth on it. This passes by the speed sensor very quickly and the speed sensor has a magnet in it and these teeth are what makes that thing generate a wheel speed signal by the number of pulses it sees. Now if this ring had messed up teeth, corrosion on the gears, or rust or something it could have been the problem. Let's hope that fixes it!

 

Thanks. I too hope that they fixed the problem. I kept thinking there may be something else being "overlooked".