No pressure in the power steering and wheel does not return

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.
© 2019 General Motors Corporation. All rights reserved.

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.

With engine running, steering turned hard right or left, can you see the fluid churn in the power steering reservoir? If not, maybe one of the power steering lines is blocked?

I just wanted to add, with some makes and models. With everything off, I remove the power steering belt. I take the return line loose from pump, aim into container, rotate the pulley by hand, see if any fluid comes out of return line? The return line should be low pressure, usually held to pump by hose clamp. The high pressure line has threaded fittings.

On a steering wheel are 2 pins. These pins turn the signals off as the wheel returns from making a left or right hand turn. They reset the blinker mechanism by bumping the blinker arm and pushing the arm back to the center position. You can sometimes see these little pins that reset the blinker if you look between the steering wheel and the steering wheel column. There is a little gap where the steering wheel is enabled to turn with out rubbing the column. You will also see a circular copper plate in there where the horn makes electrical contact by a little flat tension arm and rubs the copper surface as the wheel spins in either direction.
To repair a damage blinker pin, the steering wheel most likely has to be pulled off and the pin repaired and steering wheel returned back onto the column. Not a big job at all, just more of a pain then anything. Some steering wheels are on pretty tight on their splines and a puller may be needed. If the pins are still intact in the back of the steering wheel, then the blinker mechanism has a problem and is not be triggered to return to center by the pins.

Try turning the steering wheel (hard) right and left while turning the key. Steering lock , and ignition lock work in conjunction with each other.

check the power steering pump, if its good than it will be rack and pinion issue. the pump create a high pressure to help assist with steering, and the rack and pinion work like hydraulic cylinder which receive the pressure from the pump and the steering work like control valves. by turn left or right you controling the pressure to make the wheels turn either right or left. check and see if you have any leaks.

Did you connect the Pressure side and Return side P/S couplings on the Rack, Back to Front?
Did you refill the system and Purge the Air out of the Power Steer Lines with the Engine Running, and Sweeping the Steering from Right to Left, 2 or 3 times, at the same time?
Regards,DT

There's a technical bulletin on that from Chrysler....The power steering lines need to be replaced. I have the same problem as you see this link - http://www.wjjeeps.com/tsb.htm#STEERING

SUBJECT:
Steering Honk On 4.0L And 4.7L LHD Grand Cherokee Vehicles
OVERVIEW:
This bulletin involves the replacement of the power steering pressure
and return hoses and tube.
MODELS:
1999 - 2002 (WJ) Grand Cherokee (Domestic and International Markets)
2001 - 2002 (WG) Grand Cherokee (International Markets)
NOTE: THIS BULLETIN APPLIES TO 1999 - 2000 4.7L AND 1999 - 2002 4.0L
GRAND CHEROKEE VEHICLES THAT ARE LEFT HAND DRIVE (LHD) AND
ARE NOT EQUIPPED WITH HYDRAULIC COOLING.
SYMPTOM/CONDITION:
Some vehicles may exhibit a honk-like sound from the power steering
system. This sound occurs most often during a low speed right hand turn,
as would occur during parking lot maneuvers.
DIAGNOSIS:
If the customer indicates that the above condition is present, perform the section of
the Repair Procedure that is appropriate for the equipped engine.
PARTS REQUIRED:
Qty. Part No. Description
1 04883077 Fluid, Power Steering (MS-5931 quart)
1 05080950AA Hose, Pressure (4.7L)
1 52088116AB Fitting, Pressure Hose - Quick Connect At Pump (4.7L)
19-005-02 -2-
Qty. Part No. Description
1 05080951AA Hose, Return (4.7L)
2 **06504502** Clamp, Hose (4.0L or 4.7L)
1 **52088452AE** Hose, Pressure (4.0L)
1 **52088774AC** Hose, Return (4.0L)
1 **52088775AB** Tube, Return (4.0L)
6 **34201631** Rivet, Plastic Black (Front Fascia - 4.0L)
1 **06102141AA** Screw, Pressure Hose (6 mm - 4.0L)
REPAIR PROCEDURE:
**IF VEHICLE IS EQUIPPED WITH A 4.0L ENGINE:**
1. Remove the front fascia panel.
Fig.

sounds like the problem is in the valving in the steering box. You may have to get a new steering box. i would get it checked.