What does it mean when the note displays about the stabilty system and to service the steering system?

 

Is this a serious matter

 

in theory the system detects loss of steering control and automatically applies the brakes to help "steer" the vehicle where the driver intends to go.

how serious this is, depends on the model, the year, and such other details which are not evident in the question .. for example, it be much more serious on a SUV with a high CG than a CTS with a low CG ...

just as a note .. it is not uncommon for sensors to be damaged while being 'dragged' by the automatic car-washes and such will generate a SERVICE message, although there are other issues that will also generate the message ...



.