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.

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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 LightInstallation Procedure
Drill 8 mm (5/16 in) for plug welding along the edges of the tail lamp
pocket as noted from the original panel.
Note:
Clean and prepare the attaching surfaces for welding.
Position the tail lamp pocket on the vehicle.
Verify the fit of the tail lamp pocket.
Clamp ...
Vehicle Identification Number (VIN)
This legal identifier is in the front corner of the instrument panel, on the
left side of the vehicle. It can be seen through the windshield from outside. The
VIN also appears on the Vehicle Certification and Service Parts labels and certificates
of title and registration.
Engine Identifi ...
Installation Procedure
Clean and prepare the attaching surfaces for welding.
Position the roof rear header panel (1) on the vehicle.
Verify the fit of the panel.
Clamp the roof rear header panel into position.
Spot weld accordingly as noted from the original panel.
Apply the sealer ...