The sensor is located in the Hub assembaly. if they did not use the corect cv axle when it was replaced this light would come on. look at the axle where it enters the hub assembly and make sure you see a ring of (teeth) if not it is not the correct axle. if the axle is correct, make sure that there is no damage to the sensor from installation, or that the wires ( there are two ) are pluged in and have not been damaged. if the sensor looks to be damaged it will have to be replaced. NOTE - when the abs light is on, the abs will not function!!!