The fluid level in the pump is low.

1. Add power steering fluid, if needed. Refer to Checking and Adding Power Steering Fluid .
2. Inspect the pump for leaks.

The pump belt slips.

Replace the belt. Refer to Drive Belt Replacement in Engine Mechanical - 2.4L or Drive Belt Replacement in Engine Mechanical - 3.1L.

The pump pressure is insufficient.

Refer to Power Steering System Test .