My daughter has a 99 S-10 Blazer 4.3L 2WD. The ABS warning light has been coming on the dash especially when it get very cold out (less than 20 dgrees). The brakes are very weak and mussy. Pedal goes almost all the way to the floor like she has no brakes. If you get it up to 10-15 mph and stomp on the brakes a couple times they been coming back to normal, but not anymore. I've heard this is the wheel speed sensor gone bad? And yes, the brakes are in very good condition and nothing needs relacing like the pads, rotors, calipers,etc... Any suggestions? And how would you determine which side it is?