Power steering stops working at low speeds and while idling?

9 times out of 10 it will be the power steering pump. Here is how to replace the pump in the images below.

This guide can help as well:

https://www.2carpros.com/articles/power-steering-problems

Check out the images (below). Please let us know what happens.

The other thing it can be is the variable effort steering actuator inside the steering rack is bad. Here is information on the steering system

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 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 amp to the VES actuator which varies the amount of effort required to steer the vehicle. At low speeds, 1 amp of current is commanded to the VES actuator and the pintle valve is fully closed which provides maximum pressure and maximum steering assist for easy turning and parking maneuvers. As speed increases, current is decreased and the pintle valve opens the orifice, decreasing available pressure providing firmer steering and directional stability. 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 SYS warning message via the high speed GMLAN serial data circuit.

Yes, it can be, let's run the codes to see what comes up, you can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Here is one for about $99.00 if you need it:
https://amzn.to/3ZixY4v

Please go over these guides and report back.