(0% of the time the problem was related to the vacuum supply to an actuator. It has a vacuum hose that being exposed would fail. I would make sure it has its vacuum hose properly connected, first thing. You'll find this actuator on the front axle, ok, there is a very good instruction and complete troubleshooting explanation located right in this site, I would try to work with these instructions for all the problems you may come across. Excellent. Ok.