you need a multimeter (volt-ampere-ohmmeter)

put your tester probes on abs sensor plug and check the Ohms on it. it should show same amount of ohms in every wheel. i dont recall how many ohms it should show but it basicly dont matter, cause its very rare that more than one sensor is broken at same time. (probably its about 1.6k ohms and changes between 1.3-1.9 ohms, or something like that. but as i sayed, you dont need those values.)

then check that when you rotate the wheel, ohms will chance according how fast you rotate wheel.

if all sensors are functional, then check wiring loom to the module. take module connector out, and check from there same test that you did whit sensors. there should be same ohms than sensors.