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 steering gear is not in proper alignment to the column.

Align the steering column. Refer to Steering Column Replacement in Steering Wheel and Column - Tilt.

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 valve spool is stuck or plugged.

1. Remove the valve.
2. Clean the valve.
3. Replace the valve, if needed.

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 .