Testing front wheel speed sensors 1996

Fighting an ABS light, start and idle truck no light move about 50 feet 5mph light goes on and stays on. I see 2 front wheel speed sensors and connectors. How do I check them ? ohm meter ? or voltage read out while spinning the tire ? I do not see any sensors for the rear wheels, could there be one on the transmission ? Did not see any on the rear diff. I tried plugging and unplugging all connectors at sensors and master control unit. They all looked clean. Thanks for all replies !!

They get dirt on them.

Remove them properly , clean and reinstall.

That should be your problem.

Mine are the style that are part of the splash guard/backing plate on the inside of the rotor. They appear to be crimped in with no obvious way to remove them. Dealer list a whole assembly for about $ 170 each. They looked good from the start but used my air compressor and blew them off, no particles on them and the teeth in the exciter ring look clean blew them out also.