There have been some problems with the Electric Power Steering (EPS) on these vehicles due to power steering control module processing maximum amount of assist & overheating.
When the steering wheel is turned to its maximum rotation, the power steering control module (PSCM) will command the maximum amount of current to the EPS motor. If the steering wheel is held in this position for an extended period of time, the PSCM will go into overload protection mode to avoid system thermal damage. In this mode, the PSCM will limit the amount of current commanded to the EPS motor, which reduces steering assist levels.
If the PSCM detects a high system temperature and the overload protection mode is invoked, DTC C0176 "System Thermal Error" may be set. On some models, DTC C0476 "Electric Steering Motor Circuit Range/Performance" may also be set. These DTCs indicate normal PSCM action (reduced steering assist) to prevent thermal damage to power steering system components.
You should have your local GM dealer scan system for failure code & install the latest update calibrations.
Check under the hood ,these vehicles come with electric power steering & hydraulic power steering.I do not see many of the hydraulic power steering just "go out" unless the engine belt is thrown (which will bring on failure lights in the instrument panel cluster) or a leak to cause the pump to run dry.
I suggest checking it again later to see if the power steering has come back ,driving without power assist can be dangerous.