I have a 2009 Cadillac CTS4. I went out on a cold day to warm it up, and it started fine with no hint of trouble. When my wife went to leave she said the car was making noise and the driver information center said "service power steering" and the steering wheel would not turn.I went out a few hours later and everything worked fine, no noise and no message. The fluid level was adequate also. How does one service the power steering? Is it just a fluid change?

A customer may comment on a "Service Steering System" message on the DIC int.
Recommendation/Instructions:
Upon further diagnostics the technician may find that he has a history C0450. Please verify that the DTC is not set because of the condition called out in the latest version of PIC5272.
If all diagnostics have not lead to a repair, please check G110 on the right side of the frame rail and repair as necessary. Dealer feedback has verified a possible loose G110.
Another possible cause for the C0450may be the engine wire harnesschafing on the right cylinder heador bracket (1). This condition could result in an increase to steering efforts but not total loss of assist. It would be noticed more in parking lot maneuvers. Please review picture below.
Inspect the engine wire harnessfor chafing along the right cylinder head. Repair the wiring as necessary using SI2000 Diagnostic Information and Procedures. Protect the harness from future chafing.