The hydraulic system is faulty.

1. Diagnose the hydraulic system. Refer to Power Steering System Test .
2. Service the hydraulic system as needed.

The power steering fluid level is low.

Add power steering fluid as needed. Refer to Checking and Adding Power Steering Fluid .

The steering gear valve is sticking.

1. Flush the power steering system. Refer to Power Steering System Flushing .
2. Bleed the power steering system. Refer to Power Steering System Bleeding .
3. Replace the power steering gear if the symptoms persist. Refer to Steering Gear Replacement .

The power steering pump pressure is insufficient.

Test the power steering system. Refer to Power Steering System Test .

Replace the power steering pump. Refer to Power Steering Pump Replacement .