For 1990-2009 cars

The steering controls system is a microprocessor-controlled hydraulic power steering system. Power steering assist is determined by the microprocessor and is dependent on the vehicle speed.

The power steering control module (PSCM) constantly compares the amount of current actually flowing through the power steering fluid flow control valve actuator to the desired current it has calculated. The control valve actuator is an electro-hydraulic converter located at the valve housing of the steering gear.

The vehicle speed is transmitted to the PSCM from the EBTCM. Relative to the given speed, the PCSM determines the current for the control valve actuator and compares it to the characteristic curve programmed by the microprocessor. The electro-hydraulic converter converts the electric current into a control valve actuator position in the steering hydraulic system, which then determines the amount of hydraulic reaction and thus the steering force.

When the system is operating normally, increasing the vehicle speed will decrease the power steering assist, allowing the driver the sensation of improved road feel and directional stability. For driving in the city and for parking, increased power steering assist is encountered.