Beat cake mix, 1 cup of pumpkin, milk, oil, eggs and 1 tsp pumpkin pie spice in large bowl until well blended.
Pour evenly into prepared pans. Bake 20-22 minutes. Cool completely on wire racks.
Beat cream cheese in small bowl until creamy. Add icing sugar, remaining pumpkin and remaining 1/2 tsp pumpkin pie spice; mix well. Stir in cool whip.
Remove cake layers from pans; cut each layer horizontally in half with a serrated knife. Stack the layers on a serving plate, spreading the cream cheese mixture between the layers. Do not frost the top layer. Drizzle with caramel topping and toasted pecans.