MAGNASTEER Variable Effort Steering (VES)
The MAGNASTEER Variable Effort Steering (VES) system is made up of four components. The four components are:
| • | Electronic Brake Traction Control Module (EBTCM). |
| • | MAGNASTEER actuator. |
| • | Power Steering Gear. |
| • | Power Steering Pump. |
Electronic Brake Traction Control Module (EBTCM)
The MAGNASTEER Variable Effort Steering (VES) system has software contained in the Electronic Brake Traction Control Module (EBTCM). It processes vehicle speed information from the Antilock Brake System (ABS) wheel speed sensors to provide a control signal to the MAGNASTEER actuator located in the power steering gear.
Two Diagnostic Trouble Codes (DTCs) are stored in the EBTCM for the MAGNASTEER VES system. If DTC C1273 sets, the MAGNASTEER VES system is disabled, the ABS warning indicator lamp turns on and the ABS is disabled. If DTC C1274 sets, the MAGNASTEER VES system is disabled but, the ABS warning indicator lamp stays off and the ABS is not disabled. A difference in steering effort may be felt when a MAGNASTEER VES system DTC sets. Refer to Magnetic Steering Variable Assist (Magnasteer) for more information.
MAGNASTEER Actuator
The MAGNASTEER actuator is an integral part of the power steering gear. The MAGNASTEER actuator consists of:
| • | A permanent magnet attached to the input shaft of the rotary valve. |
| • | Two pole pieces attached to the output side of the valve (the pinion). |
| • | An electromagnetic coil mounted in the gear housing. |
When the electromagnetic coil is energized, a magnetic field is formed between the permanent magnet and the pole pieces, which increases the torque on the input shaft to the steering gear. The Electronic Brake Traction Control Module (EBTCM) controls current flow to the electromagnetic coil and as vehicle speed increases, current flow control from the EBTCM increases, and the steering effort increases.
Other power steering system components, while specially modified for use with the MAGNASTEER Variable Effort Steering (VES) system, are similar to non-MAGNASTEER VES power steering components.
Power Steering Gear
Except for differences in valve machining, the design of the MAGNASTEER Variable Effort Steering (VES) power steering gear assembly is the same for a non-MAGNASTEER VES system. 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 steering gear 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 to move the rack left or right. The rotary control valve regulates the amount of effort by responding to the driver's torque input.
Power Steering Pump
A constant displacement vane-type pump provides hydraulic pressure and flow for the power steering system. The pump is belt driven by the power steering pump and engine crankshaft pulley. There is an opening at the rear of the pump housing, containing the pump ring, pressure plate, thrust plate, rotor, vanes, and end plate. A small opening on the side of the housing contains the pressure line fitting. A pressure relief valve inside the flow control valve limits the pump pressure.
