HouseCallAuto 11/6/2012You cannot guess at it. you need to know the fault code that is stored in the abs module. The usual cause can be a bad front wheel speed sensor but hey, there is a left and a right. You cannot possible know which one is your cause. You have a 50/50 chance. If the left one was replaced in '09 then it would be more likely that the right one would be the cause this time, buy hay, ya never know. My advice, have someone with a code reader that is able to read gm abs codes read the codes for ya. or buy your own abs code reader and read them yourself.