After you have tested the continuity as Michael describes, switch your meter to A/C volts and spin the wheel slowly. You should get a constant voltage only changing with speed. The amplitude of this reading should be within 10% of the same thing done to the other side.
I do this test with the Bosch tester while driving very slowly through our parking lot. By doing it while driving and switching back and forth between sensors its easy to see the differences. Bosch doesn't recommend driving with the tool on. For years we missed these diagnosis because it is too hard to get a good comparison when you spin one wheel at a time.
I doubt that you will find a continuity problem, as such a problem would turn the light on without driving and wouldn't care about speed as to whether the event occured. The reason it happens at low speed is that is the most critical time for sensor signal strength comparisons. You will notice that at some speed the amplitude will peak. This happens at around 2-4mph and its usually at lower speeds where full amplitude isn't achieved that the sensor differences trigger the fault recognition.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician