TOD Light ABS Help

I recently took my VX in because the ABS light came on and the TOD Check light was flashing. The first code said the Electronic Hydraulic Control Unit was bad. I replaced it for about 150 from a junk yard. That cleared the EHCU code. The other code is for the Rear differential sensor. (Repair shop called it the Rear Differential ABS Sensor) do they mean the rear differential speed sensor? They said it would cost $585 new from Isusu. Is there anywhere I can buy the part cheaper.(www.car-parts.com) Does anyone know the exact name of the part I am describing?

Much Thanx

As an ex Ford parts person for 30 years. I'd call it a differenial speed sensor. They are also used on some vehicles to supply info for the speedometer. If you are doing a car-parts search, try a rear axle search. I'd bet it's the same on a Trooper, so try that axle search and call whoever comes up and ask them to check the axle housing for it. They are usually mounted on top of the differential into the case. There's a small ring gear inside whose spinning teeth are what the sensor reads. They can also be located at the axle end, picking up the ring mounted on the backside of the hub and rotor.

Any chance there's an electrical connector for the sensor that just needs to be cleaned?