Buick Enclave: Description and Operation

POWER STEERING SYSTEM DESCRIPTION AND OPERATION

The hydraulic power steering pump is a constant displacement vane-type pump that provides hydraulic pressure and flow for the power steering gear. The hydraulic power steering pump is either belt-driven or direct camdriven.

The power steering fluid reservoir holds the power steering fluid. The power steering fluid reservoir may be integral with the power steering pump or remotely located. The vehicle may have a combination of a power steering fluid reservoir integral with the power steering pump and a remotely located power steering fluid reservoir. The following locations are typical locations for the remote reservoir:

• Mounted to the front of the dash panel
• Mounted to the inner fender
• Mounted to a bracket on the engine

The 2 basic types of power steering gears are listed below:

• A recirculating ball system
• A rack and pinion system

In the recirculating ball system, a worm gear converts steering wheel movement to movement of a sector shaft.

A pitman arm attached to the bottom of the sector shaft actually moves one tie rod. An intermediate rod moves the other tie rod.

In the rack and pinion system, the rack and the pinion are the 2 components that convert steering wheel rotation to lateral movement. The steering shaft is attached to the pinion in the steering gear. The pinion rotates with the steering wheel. Gear teeth on the pinion mesh with the gear teeth on the rack. The rotating pinion moves the rack from side to side. The lateral action of the rack pushes and pulls the tie rods in order to change the direction of the vehicle's front wheels.

The power steering pressure hose connects the power steering pump union fitting to the power steering gear and allows pressurized power steering fluid to flow from the pump to the gear.

The power steering return hose returns fluid from the power steering gear back to the power steering fluid reservoir. The power steering return hose may contain an integral fin-type or line-type power steering fluid cooler.

In a typical power steering system, a pump generates hydraulic pressure, causing fluid to flow, via the pressure hose, to the steering gear valve assembly. The steering gear valve assembly regulates the incoming fluid to the right and left chambers in order to assist in right and left turns.

Turning the steering wheel activates the valve assembly, which applies greater fluid pressure and flow to 1 side of the steering gear piston and lower pressure and flow to the other side of the piston. The pressure assists the movement of the gear piston. Tie rods transfer this force to the front wheels, which turn the vehicle right or left.

VARIABLE EFFORT STEERING SYSTEM DESCRIPTION AND OPERATION

The Variable Effort Steering (VES) 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 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 controls the actuator using 0 to 1.0 Amp. At 0 mph the EBCM supplies 1.0 Amp to the actuator. As the vehicle speed increases the amperage to the actuator decreases. The VES 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 VES actuator. The EBCM has the ability to detect malfunctions in the VES actuator or the circuits to the actuator.

Any malfunctions detected will cause the VES outputs to be disabled and the actuator will return to an open state. The EBCM will command the driver information center (DIC) to display the SERVICE STEERING SYSTEM warning message via a serial data circuit.

SPECIAL TOOLS AND EQUIPMENT

SPECIAL TOOLS

CH-6321
J-34028
KM-6321
Inner Tie Rod Wrench

CH-22610
J-22610
KM-J-22610
SA9164C
Keystone Clamp Pliers

CH-24319-B
7503
J-24319-B
SA91100C
Tie Rod Separator

CH-25033-C
8996415
J-25033-C
KM-J-25033-C
SA9162C
Pulley Installer

CH-25034-C
J-25034-C
KM-J-25034-C
SA9162C
Pulley Remover

CH-39570
J-39570
Chassis Ear

CH-43485
J-43485
Power Steering Bleeder Adapter

CH-44721
J-44721
Power Steering Analyzer

CH-48600
Power Steering Analyzer Adapters

GE-8001
J-8001
Dial Indicator Set

GE-23738-A
30 14 883
J-23738-A
J-35555
MKM-667
SA9180NE
Vacuum Pump

GE-28431-6
J-28431-6
Fluorescent Oil Dye 6 1 oz

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