Circuit Description

The variable effort steering (VES) diagnostic system check is an organized approach to identify problems associated with the Magnetic Steering Variable Assist (MSVA) system also known as MAGNASTEER®. The MSVA system varies the driver effort required to steer as the vehicle 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. MSVA accomplishes this by adding or subtracting torque in the rotary input shaft to the power rack and pinion. When the vehicle is stationary, MSVA adds torque to assist the driver in turning the steering wheel. As the vehicle speed increases, the torque provided by MSVA decreases. MSVA increases resistance to the turning of the steering wheel for improved road feel at higher speeds. The electronic brake control module (EBCM) controls the current to the MSVA actuator to increase or decrease the torque provides by the actuator. The EBCM uses the inputs from the ABS wheel speed sensors and the steering wheel position sensor to calculate the amount of torque applied by the MSVA actuator.