I have a 92 Full Size Blazer. The ABS Light comes on when speed exceeds 15mph. As soon as the speed is below 15mph, the ABS light goes out. I checked/cleaned the speed sensors earlier today (took voltage measurements on the speed sensor back at the plug on the ABS unit, volts varied between .5 volts and 4.5volts AC depending upon speed of the drive shaft). I have a scanner/code reader (Auto X-ray 3000) but it does not pick up ABS codes (wasn't showing any problems). I do not get the any other warning lights (check engine, parking brake, etc.) Is the next step trying to figure out which ABS code is being sent? Or is there some other preliminary things to look at prior to figuring out the code? Thanks for the help.