The fluid level in the pump is low.

Add power steering fluid, if needed.

Refer to Checking and Adding Power Steering Fluid .

The pump belt slips.

Refer to Drive Belt Replacement in Engine Mechanical - 2.2L or Drive Belt Replacement in Engine Mechanical - 2.4L.

Internal leakage in the steering gear or the pump is high.

Refer to Power Steering System Test

The flow control valve sticks closed.

Refer to Power Steering System Test .