The tires are under-inflated.

Inflate the tires to the specified pressure. Refer to Tire Inflation Pressure Specifications in Maintenance and Lubrication.

Binding is present in the following components:

Replace any parts, if needed. Refer to Suspension General Diagnosis in Suspension.

The suspension ball joints and the steering linkage lack lubricant.

Lubricate the suspension ball joints and the steering linkage. Refer to Explanation of Scheduled Services in Maintenance and Lubrication.

The front wheels are not in alignment.

Inspect the wheel alignment. Refer to Wheel Alignment Specifications in Wheel Alignment.

The return hose has a kink.

Replace the hose. Refer to Power Steering Hoses Replacement .