This light functions for both the parking (emergency) brake and the foot brake systems. If the light is on all the time, it could simply mean the parking brake is still on or lever is misadjusted. The brake warning light remains on when the brake is set as a reminder. If the brake warning light remains on when the parking brake is released, then your brakes may need to be serviced.
If the brake warning light comes on when you apply the brakes, or is on continuously, it may mean that hydraulic pressure has been lost in one side of the brake system or that the fluid level in the master cylinder is dangerously low (due to a leak somewhere in the brake system). In either case, the fluid level in the master cylinder should be checked. Adding brake fluid to the master cylinder reservoir may temporarily solve the problem. But if there’s a leak, the new fluid will soon be lost and the warning light will come back on.
Brake fluid leaks are serious because they may cause the brakes to fail! So avoid driving the vehicle until the system can be inspected to determine what’s wrong. Leaks can occur in brake hoses, brake lines, disc brake calipers, drum brake wheel cylinders or the master cylinder itself. Wet spots at hose or line connections would indicate a leak that needs to be fixed.
Leaking brake fluid can also contaminate the brake linings, causing them to slip or grab. The uneven braking action that results may cause the vehicle to veer to one side when the brakes are applied. Brake shoes or pads that have been contaminated with brake fluid cannot be dried out and must be replaced.
Parking brake indicator:
When the ignition switch is in the ON position, the light comes on when the parking brake is applied.