its probably just your float.. pull it out by removing the plate thats covering your gas tank and check to make sure its not bent or binding up or anything.. should be able to get one for pretty cheap.. if you have a buddy that will let you tinker with there car you can messure the signal that is being sent out by the float when its at full tank and comapair to yours to give you an idea on whats going on and if the sensor is bad or not..