Can not get the pinion arm/balljoint separated from the power steering control valve

Question edited for clarity and dreadful spelling of 'Cadillac'.
Question moved to model category.

Yes it does have power steering.

https://www.google.com/search?q=2009+Cadillac+DTS+power+steering

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Which power steering system does your vehicle have ? EPS - electric power steering or hydraulic power steering . Do you have a EPS light lit on the instrument cluster ?

Power Steering System Description and Operation (EPS)
The power steering system reduces the amount of effort needed to steer the vehicle. The system uses the powertrain control module (PCM), body control module (BCM), power steering control module (PSCM), discrete battery voltage supply circuit, steering shaft torque sensor, steering wheel position sensor, power steering motor, driver information center (DIC), and the serial data circuit to perform the system functions. The PSCM and the power steering motor are serviced as an assembly and are serviced separately from the steering column assembly. The steering shaft torque sensor and the steering wheel position sensor are not serviced separately from each other or from the steering column assembly. The steering column assembly does not include the power steering motor and module assembly.

Power Steering System Description and Operation (HPS)
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 pumps are either belt-driven or direct-drive, cam-driven.
The power steering fluid reservoir holds the power steering fluid and may be integral with the power steering pump or remotely located. 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 and an intermediate rod move 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 line 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 one 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.
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steering rack or gear . 2X2 - 4X4 engine . Depends on steering system .
When you turn the steering wheel, the steering gear rotates the pitman arm which forces the relay rod to one side. The tie rods connect to the relay rod with the ball studs. The tie rods transfer the steering force to the wheels. Use the tie rods in toe adjustments. The tie rods are adjustable. The pitman arm support the relay rod. The idler arm pivots on a support attached to the frame rail and the ball stud attaches to the relay rod.
The 2 tie rod are threaded into the tube and secured with jam nuts. Right and left hand threads are used in order to permit the adjustment of toe.

Binding linkage , steering gear worn etc....

Power Steering System Description and Operation (w/o Electro-Hydraulic Steering)
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 pumps are either belt-driven or direct-drive, cam-driven.
The power steering fluid reservoir holds the power steering fluid and may be integral with the power steering pump or remotely located. 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 and an intermediate rod move 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 line 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.


Your best bet , take it to a qualified repair shop.

just tighten the bolt or change the copper washers first two of them.

There are two ways:
1. Pickle fork ball joint seperator. ( It will damage the dust boot.)
2. Look at some of these: https://www.youtube.com/watch?v=feKKmmSJ2ZA&feature=related

The ball joints are located in the the steering knuckle below the axles and the balljoint stud goes through the lower control arms. <a href= Balljoint">http://cdn-viper.demandvideo.com/media/87FD3A7E-BAFA-4A84-818E-EF8F26E3B1BB/jpeg/76826C4A-1DBE-4F1A-B5BC-5B559EE58878_3.jpg>Balljoint location</a> here is a pic courtesy of ehow.com

maybe the steering rack or lower arm balljoint

replace the entire CV axles. Support vehicle with jackstands by frame. Remove front wheels. Remove axle nuts. Remove lower balljoint nut. Separate balljoint from nuckle by banging hard with ball peen hammer on knuckle on spindle assy. Remove outer tie-rod nut. Separate tie-rod from steering nuckle by bangin on nuckle with ball-peen hammer. Use long pry bar to hold lower control arm down while simultaneously pulling hub/spindle assembly away from vehicle and pushing axle through hub toward transaxle. Go under vehicle and pry inner cv joint away from transaxle while holding axle assembly.
Install new CV axle in reverse of the disassembly.

Check and fill power steering fluid. If this won't help the power steering pump might be faulty.

Loosen the wheel nuts on both wheels, jack-up the car, and support on jack-stands.Take out both front tires. Detach the stabilizer link from the control-arm, remove the ball-joint clamp bolt and nut. Separate the balljoint stud from the steering knuckle with a big screw-driver. Remove bolts that's holding the control-arms to frame.