A downhole tool and system for actuation of the tool. The tool includes a sliding sleeve assembly that is urged toward an opening position due to an interior pressure in the tool. A shear pin assembly hold the tool in the closed position. As pressure is increased to above a predetermined locking set point, a locking mechanism on the sliding sleeve radial engages the housing of the tool to lock the sliding sleeve to the housing. As pressure is further increased to a predetermined an activation set point, the shear pin assembly shears, but the sliding sleeve is maintained in the closed position by the locking mechanism. Only after the interior pressure is subsequently lowered to below a predetermined opening set point will the sliding sleeve shift to an open position.