I agree, with GMtech1.....need to have the codes read with an ABS scanner/reader.....once you know what wheel caused the problem, you can do an ohm check and an a/c check......but that only checks out when the problem is happening, not if intermittent......once you know what wheel is the problem, disconnect the harness from the sensor and shake it......if water comes out of the harness, water intrusion could cause you to replace the harness AND the sensor....