Checking Brake Fluid
You can check the brake fluid without taking off the cap.

Look at the brake fluid reservoir. The fluid level should be above MIN. If it is not, have your brake system checked to see if there is a leak.
After work is done on the brake hydraulic system, make sure the level is above the MIN, but not over the MAX mark.
See also:
Reporting Safety Defects to the
United States Government
If you believe that your vehicle has a defect which
could cause a crash or could cause injury or
death, you should immediately inform the National
Highway Traffic Safety Administration (NHTSA)
...
OnStar®
If equipped, this vehicle has a
comprehensive, in-vehicle system
that can connect to a live Advisor
for Emergency, Security, Navigation,
Connection, and Diagnostic
Services. See OnStar Overv ...
Auxiliary Devices
This vehicle may have a 3.5mm (1/8 in) auxiliary input jack and a USB port, located in the center console. Some portable audio devices such as iPods®, MP3 players, and USB storage devices can be conn ...
