Your vehicle has either hydraulic or air brakes. Each system has different warning lights.
Vehicles with hydraulic brake systems have two brake system warning lights on the instrument panel.
If the brake warning light comes on, it means that the fluid level in the master cylinder reservoir is low or there is another problem with your hydraulic brakes.
When it comes on, you will also hear a warning tone.
This light should come on briefly when you turn the ignition key to ON/RUN. If it does not come on, then have it fixed so it will be ready to warn you if there is a problem.
The brake warning light may come on, and the warning tone may sound, when you are turning and braking at the same time. This is normal. See "Hydraulic Brake Systems" under Braking.
Your vehicle has a brake warning light. When the ignition is on, this light will come on when you set your parking brake. The light will stay on if your parking brake does not release fully.
This light should also come on when you turn the ignition key to START. If it does not come on then, have it fixed so it will be ready to remind you if the parking brake is applied or has not released fully.
Vehicles with air brake systems have a brake system warning light on the instrument panel.
The low air warning light should come on, as a check, whenever you start the engine.
However, it is designed to come on, and stay on, when brake reservoir pressure has dropped below 60 psi (410 kPa).
When the warning light comes on while you are driving, you should drive only as far as the nearest point of safety and then stop the vehicle. Here is a very important thing for you to know:
Caution: If the air brake system warning light comes on and the warning tone sounds, the vehicle can stop suddenly and without further warning. This is because the parking brake will come on if the pressure falls below 35 to 45 psi (240 to 310 kPa). You or others could be injured. If the air brake system warning light comes on and the warning tone sounds, stop as soon as you can. You will not know how quickly the system is losing pressure, so be aware that the parking brake may come on suddenly.