For 1990-2009 cars

A variable effort steering electrical system malfunction causes the power steering fluid flow actuator to default to a full restriction. A full restriction increases the steering effort. Refer to Variable Effort Steering System Check if the vehicle is experiencing this condition.

A mechanical/hydraulic steering system malfunction causes the loss of power steering at all times and/or objectionable noises.

Refer to Power Steering System Test if a mechanical or a hydraulic malfunction of the pump or the steering gear is suspected.