Electro-Hydraulic Solenoid Control
The GM monitors the road speed input and supplies the electro-hydraulic solenoid with power. The road speed signal "A" is supplied from the IKE (and K-Bus) on E38 vehicles and from the DSC Control Module on E39/E53 vehicles.
The solenoid is pulse width modulated for control and varies the amount of assist based on the road speed. The maximum assist is available while parking and driving at slow speeds.