For 1990-2009 cars

The Variable Effort Steering (VES) system varies the driver effort required to steer as vehicle speed changes. At low speeds, the system provides maximum power assist for easy turning and parking maneuvers. At higher speeds, steering assist is decreased to provide the driver with firmer steering (road feel) and directional stability.

The VES system accomplishes this by reducing power steering fluid flow from the pump as vehicle speed increases. When the vehicle is stationary, the system provides maximum flow. As vehicle speed increases, fluid flow is decreased.

### Component Description

The VES system is made up of the following special power steering components:

• | Electronic Brake Control Module (EBCM)

• | Power Steering Pump Actuator

• | Steering Wheel Position Sensor

• | Power Rack and Pinion

• | Power Steering Pump

### Electronic Brake Control Module (EBCM)

The VES steering system has software contained in the Electronic Brake Control Module (EBCM). It processes vehicle speed information from the ABS wheel speed sensors and uses the steering wheel position sensor to provide a control signal to the power steering pump actuator on the power steering pump.

### Power Steering Pump Actuator

The power steering pump actuator assembly at the power steering pump discharge fitting contains an electronic variable orifice (EVO) solenoid-operated pintle valve. Fluid leaving the pump passes through an orifice in the actuator tip. When the solenoid is grounded by the EBCM, it moves the pintle into the orifice, reducing power steering fluid flow. As vehicle speed increases, the pintle restricts the orifice proportional to the speed of the vehicle.

(1) | Discharge Fitting
(2) | O-Ring Seal (Small)
(3) | O-Ring Seal (Large)
(4) | Power Steering Pump Actuator
(5) | Power Steering Pump Actuator Connector Position Clip

Other power steering system components, while specially modified for use with the VES system, are similar to non-VES power steering components.

### Steering Wheel Position Sensor

The steering wheel position sensor is an input to the EBCM. The sensor monitors the steering shaft position and the rotational speed.

(1) | Lower Spring Retainer
(2) | Steering Wheel Speed Sensor
(3) | Lower Bearing Spring
(4) | Lower Bearing Seat
(5) | Adapter and Bearing Assembly
(6) | Steering Column Jacket Assembly

### Power Rack and Pinion

Except for differences in valve machining, the design of the VES power rack and pinion assembly is the same as a non-VES system. As with non-VES steering, the steering wheel movement is transferred to the pinion; the pinion moves the rack left or right through meshing pinion and rack teeth; the force is then transmitted through the tie rod ends and steering knuckles to steer the wheels.

The power rack and pinion steering system has a rotary control valve which directs hydraulic fluid (from the power steering pump) to one side or the other side of the rack piston. The piston is attached to the rack, and uses hydraulic pressure in order to assist the rack movement left or right. The rotary control valve regulates the degree of assist by responding to the driver's torque input.

If hydraulic assist is not available, manual control is maintained. However, under this condition, more driver steering effort is required.

### Power Steering Pump

The standard vane-type pump, which provides hydraulic pressure for the system, incorporates a special discharge fitting to hold the EVO actuator.