Air is present in the system.

1. Add power steering fluid to the power steering reservoir. Refer to Checking and Adding Power Steering Fluid.
2. Bleed the system. Refer to Bleeding Power Steering System.
3. Inspect the hose connectors for proper torque or damaged seals.

The steering gear mounting is loose.

Tighten the attaching bolts to the specified torque. Refer to Fastener Tightening Specifications.

There is a worn or damaged steering gear.

Replace the steering gear. Refer to Power Steering Gear Replacement.