Explain why car brake lights are on

Many people often think that when the brake light is on, it means the brakes are working, so there is nothing to worry about. However, behind that light signal is a problem that needs to be paid attention to by the car owner.

On some car models, the handbrake usually has its own symbol in the shape of a P with a circle in the middle. If the user sees the brake warning light on and flashing continuously even when the brake is pressed or not, the brake system must be checked immediately and the system must be refilled with oil.

According to the explanation of experienced car experts, the cause of this phenomenon may be due to the loss of brake pressure to the cylinders or the oil level in the reservoir is too low. If the oil level is low, the sensor will transmit a signal to the ECU, then the ECU will control the brake warning light.

In addition, oil may leak in the system such as: master cylinder, slave cylinder or brake lines. Therefore, you need to check the warning light, otherwise the light will come back on. The consequences of this leak can be dangerous for the driver, causing brake failure while driving.

Hydraulic circuit in brake system

For front-wheel drive vehicles: there are two hydraulic circuits: one circuit applies to the front brake assemblies, the other circuit applies to the rear brake assemblies.

For rear wheel drive vehicles one circuit is used for the front left and rear right brake assemblies, the other circuit applies to the front right and rear left brake assemblies.

This arrangement is intended to provide safety assistance in the event of a failure, as if one circuit loses brake pressure, the other circuit will assist in slowing down. Furthermore, the oil pressure switch is installed on the master cylinder or on the oil line behind the master cylinder. If a leak occurs in either circuit, the switch will illuminate the brake warning light.

ABS brake warning light

Nowadays, most new modern cars are equipped with anti-lock braking system (ABS), this system is equipped with a separate warning light. Under normal operating conditions, the light only lights up when the key is turned on and when the engine is started, otherwise the light will be off.

Thus, when the vehicle is running and the user sees the light on, it means there is damage in the ABS system, although it still works normally except in emergency situations. When an unexpected incident occurs, the ABS will not work and is prone to slipping.

There is also a case called “nonlatching” error because the warning light comes on and then goes off and the ABS system still works normally. This case is not serious so the car owner does not need to worry too much.

In particular, thanks to the system memory, errors occurring in the ABS will be saved as a code and can be read by a diagnostic machine. Thereby, repair work is also easier.