AutoNavi will remind you that there is a road that can take 20 minutes faster when driving to the fast-forward mountain. Just choose that road. It is not a county road or a provincial road.
Take the Sansan Provincial Highway from Liangnong Town, and navigate all the way through the Jingbai Line (two scenic spots along the way if you are interested: Danshan Chishui Scenic Spot and Shilin Village), to Simingshan Town Forest Park, Yangtian Lake, and finally to the Geological Park...Zhezhong Drunk Beautiful Panshan Highway
Using AutoNavi, if you arrive at the Geological Park via Yuyao Liangnong, Shanghai will automatically guide you to the Panshan Highway, just like the small road you used to test.