After you have the wiper motor area open, turn on the wipers and watch the unit cycle, especially through the turning the switch to off position. The tab is on the transmission area closes to the front of the vehicle and the arms are on the other side. The tab hits another metal tab at the 5 o'clock location. But if this tab is pushed inward, it will not hit on the other tab. Once you find this tab and take a screw driver to pry it outward. Cycle the wipers again and when turning them off again, the two tabs will make contact and it will change the direction of the wipers. If you get it to this stage, you are all set. If not, keep watching the cycle in the off position, that is the most important to watch so you can figure it out easier. You can ask a GM parts guy too from this point as well.