01 ABS Light On

hello , i have a 2001 Jimmy 4x4. my abs light is on. I removed both front sensors and cleaned & reinstalled them . the light went out for 2 days & is now back on. Sometimes it goes out for awhile but then comes on again. I've metered the ohms across the sensors one is 1.098 the other is 1.198. does any body know which is correct? or are they both ok? the 1.198 has been replaced when i put a new front hub assembly in about a year ago. My haynes book says to look in one of their chapters for the sensors specs but i can't find any spec for the speed sensors. Also where is the rear wheel sensor its suppose to be in the trasnfer case in mine. could that be bad? I've also cleaned the connections at the abs controll unit.thanks
george