P215A Vehicle Speed/Wheels Speed Correlation

[JMA1181]

When my ABS light comes on this is the code I get (P215A). Does anyone know what the issue may be? Also, sometimes after the light goes out when I put on the brakes the pedal pushes back as if the ABS is kicking on but it goes to normal after it pushes the pedal back to me. I have read about the sensors going bad, but would this be sensor related? If so, which sensor is it that needs to be replaced?
Thanks, Jordan