I know this is old, but what I just found out might help someone with an ABS light. My son was pulling a trailer with the 97 4X4 Expedition rust bucket and had to stop quickly a few times. The front brakes started smoking and shortly after, the ABS light came on and the brake peddle would pulsate. The brakes worked OK, but the light stayed on because the ABS was disabled. The system would reset and the light would go out after a new start-up, then at like 10mph it would come back on. My scanner said Code C1234, right front signal blah blah blah. I replaced the sensor and it did the same thing. After tracing/ohm-ing all the ABS wires for a break or short to ground or corrosion, to the ABS module all was good.
When I looked into the hole for the sensor on the hub I noticed the gear (Tone ring or some crap) that the sensor picks up the signal from was coated with globs of grease. Apparently it isn’t supposed to be covered with grease. I am assuming that when he smoked the brakes it heated the hub so much that the seals melted in the bearings allowing the melted hot grease to leak out and cover the gear. The wheel didn’t have much if any play in it so I thought it was OK. I called a Ford mechanic buddy and he said he replaces the hubs all the time for the trucks and crown vics and they come with the sensor. I found an aftermarket hub on-line for 85 bux and took a chance and replaced it. Before I put it on I took out the sensor on the new one and the gear was clean and no grease.
Replaced it, reset the light and no more ABS light.
So if you are getting a code for a wheel sensor, I would pull it look inside the hole to see if the gear is coated with grease before you buy a sensor. Assuming that you checked all the wiring first to rule that out. All and all, an easy job.
