Rep Power: 0

I have an 02 Civic that has had the ABS light on for some time now. Last night i jumped pins 4 to 9 in the ODBII harness to access the diagnostic mode and the ABS light flashed 1 long, 3 short, indicating code 13. which my research indicates means "Open circuit in left hand front wheel speed sensor"

just looking for clarification as to what this could mean, as my previous inspection/testing of that sensor indicated that it should be working.. Would brake dust build up cause a sensor to fail or is it more likely a faulty sensor/wiring issue? not 100% sure how the speed sensors pick up their signal, but i tested both the left and right for continuity and neither one indicated a current, should they?

Have been looking all over for some info on this, anything anyone can offer would be greatly appreciated!