The vehicle brake system consists of two hydraulic circuits. If one circuit is not working, the remaining circuit can still work to stop the vehicle. For normal braking performance, both circuits need to be working.
If the warning light comes on, there is a brake problem. Have the brake system inspected right away.

Metric

English
The brake indicator light should come on briefly as the engine is started. If it does not come on have the vehicle serviced by your dealer.
WARNING
The brake system might not be working properly if the brake system warning light is on.
Driving with the brake system warning light on can lead to a crash. If the light is still on after the vehicle has been pulled off the road and carefully stopped, have the vehicle towed for service.
If the light comes on while driving, a chime sounds. Pull off the road and stop. The pedal might be harder to push or go closer to the floor.
It might also take longer to stop.
If the light is still on, have the vehicle towed for service.
Malfunction Indicator Lamp
Antilock Brake System (ABS) Warning LightFront Side Door Window Adjustment
Warning: Refer to Glass and Sheet Metal Handling Warning in the Preface
section.
Warning: Refer to Express Window Down Warning in the Preface section.
Preliminary Procedure
Remove the front side door trim. Refer to Front Side Door Trim
Replacement.
Remove the water deflector. Refe ...
Test Probe Caution
Caution: Do not insert test equipment probes (DMM etc.) into any
connector or fuse block terminal. The diameter of the test probes will
deform most terminals. A deformed terminal will cause a poor connection, which
will result in a system failure. Always use the EL-35616
GM-Approved Terminal T ...
Air/Wind Noise
Special Tools
CH-39570 Chassis Ear
GE-41416 Ultrasonic Leak Detector
Warning: Refer to Assistant Driving Warning in the Preface section.
To analyze a reported windnoise condition, test drive the vehicle to
determine the origin of the noise.
Choose a regular route with smooth and strai ...