The variable assist magnetic steering system (Magna Steer) varies the driver effort required to steer the vehicle as speed changes. At low speeds, the system requires minimum steering effort for easy turning and parking maneuvers. Steering effort is increased at higher speeds in order to provide the driver with firmer steering (road feel) and directional stability. The EBCM controls a bi-directional magnetic rotary solenoid. The solenoid is located in the steering gear. The EBCM varies the steering assist by adjusting the current flow through the solenoid. The solenoid adjusts the amount of power steering assist in order to achieve a given level of driver effort to turn the vehicle.

MagnaSteer® accomplishes this by adding or subtracting torque on the rotary input shaft to the power rack and pinion. The amount of steering assist is dependent upon vehicle speed. As the vehicle speed increases, the following actions occur:

As the vehicle speed decreases, the following actions occur:

The variable effort steering (VES) system uses inputs from the ABS wheel speed sensors and steering wheel position sensor to the EBCM to determine the desired amount of power steering assist.

The EBCM has the ability to detect malfunctions in the steering wheel position sensor, the actuator or the circuitry to those components. Any malfunction detected will cause the power steering assist to remain at maximum with the pintle in its normally retracted position for all speeds.

When the system is operating normally, increasing the vehicle speed will decrease power steering assist, allowing the driver to have improved road feel and directional stability. When the EBCM steering wheel position sensor detects sudden steering maneuvers, the EBCM reduces the actuator current in order to provide maximum steering assist.

When the Electronic Brake Control Module (EBCM) commands the Magnasteer® Actuator ON, battery positive voltage is supplied through the EBCM to the MAGNASTEER® actuator . Ground/control for the MAGNASTEER® actuator is provided through the EBCM to MAGNASTEER® actuator controls the amount of current supplied to the MAGNASTEER® actuator based on the input from the wheel speed sensors.

The variable power steering system has 3 response modes. Use the scan tool to adjust the system per the customer request. Refer to Vehicle Personalization .

At the heart of the system is an electromagnetic actuator, which consists of a multiple-pole ring-style permanent magnet (that is attached to, and rotates with, the spool shaft or the input side of the system), a pole piece (that is attached to, and rotates with, the pinion or the output side of the system), and an electromagnetic coil assembly.

When the electronic controller senses the vehicle's speed, it generates an electrical current that is most appropriate for each speed. This current then energizes the electromagnetic coil, which causes the permanent magnet to seek alignment in relationship to the pole piece. (Note: Field strength increases with a higher current to increase the relative force between the permanent magnet and the pole piece.) Again, depending on the polarity of the current in the coil, the system, the current immediately ramps to 0 amps to provide a mid-range effort level. (Note: Currently, the principal input into the controller is vehicle speed. Other inputs may be added, such as steering wheel position, to derive lateral acceleration).