Low oil level in the power steering pump.

Check and add power steering fluid, if necessary. Refer to Checking and Adding Power Steering Fluid .

The power steering pump belt is slipping.

Inspect the drive belt for wear. Refer to Drive Belt Tensioner Diagnosis in Engine Mechanical.

There is internal leakage present in the steering gear or the pump.

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

The flow control valve is sticking closed.

Remove and clean or replace the valve. Refer to Power Steering Pump Flow Control Valve Replacement - Off Vehicle .