Vauxhall Workshop Service and Repair Manuals

Variable Effort Steering System Description and Operation

The variable effort steering system varies the amount of effort to steer the vehicle as wheel speed changes or lateral acceleration occurs. The electronic brake control module (EBCM) controls an actuator located in the steering rack and pinion. The actuator consists of an electromagnetic coil and a normally open pintle valve. The valve regulates an orifice that bleeds inlet pressure through a return passage to regulate the amount of pressure available for steering assist. The EBCM commands current from 0-1 A to the variable effort steering actuator which varies the amount of effort required to steer the vehicle. At high speeds, 1 A of current is commanded to the variable effort steering actuator and the pintle valve is fully closed which provides minimum pressure for a firm steering feel and directional stability. The variable effort steering system uses the steering wheel position sensor input to calculate lateral acceleration during abrupt driving maneuvers. The system also uses the antilock brake system (ABS) wheel speed sensor inputs to determine vehicle speed. The EBCM is constantly monitoring these inputs to achieve the desired current to the variable effort steering actuator. The EBCM has the ability to detect malfunctions in the variable effort steering actuator or the circuits to the actuator. Any malfunctions detected will cause the variable effort steering outputs to be disabled, and the actuator will return to an open state. The EBCM will command the driver information center to display the SERVICE STEERING SYSTEM warning message via a serial data circuit.