If the red brake warning lamp lights up in the instrument cluster and you hear a warning tone while the engine is running, the brake fluid level may be too low.
Observe additional warning messages in the multifunction display.
The brake fluid level may be too low due to brake pad wear or leaking brake lines.
Have the brake system checked immediately. This work should be carried out at an authorized Mercedes-Benz Center.

All checks and maintenance work on the brake system must be carried out at a qualified specialist workshop. This work should be carried out at an authorized Mercedes-Benz Center.

Have the brake pads replaced and the brake fluid renewed at a qualified specialist workshop, e.g. an authorized Mercedes-Benz Center.

WARNING
If brake pads or brake fluid other than those recommended are used, the braking properties of the vehicle can be degraded to an extent that safe braking is substantially impaired. This could result in an accident.

Vehicles with 4MATIC: function or performance tests may only be carried out on a 2-axle dynamometer. If you are planning to have the vehicle tested on such a dynamometer, contact an authorized Mercedes-Benz Center to obtain further information first. Otherwise, you could damage the drive train or the brake system.

Vehicles with 4MATIC: as the ESP® system operates automatically, the engine and the ignition must be switched off (SmartKey in position 0 or 1 in the ignition lock or Start/Stop button in position 0 or 1) when the electric parking brake is being tested on a brake dynamometer.
Braking maneuvers triggered automatically by ESP® may seriously damage the brake system.

Vehicles with 4MATIC: as the ESP® system operates automatically, the engine and the ignition system must be switched off (SmartKey in position 0 or 1 in the ignition lock or Start/Stop button in position 0 or 1) when:
• testing the electric parking brake on a brake dynamometer.
• you intend to have the vehicle towed with one of the axles raised.
Braking maneuvers triggered automatically by ESP® may seriously damage the brake system.

If your brake system is subject only to moderate loads, you should test the functionality of your brakes at regular intervals by pressing firmly on the brake pedal at high speeds. This improves the grip of the brake pads.

WARNING
Make sure that you do not endanger other road users when you apply the brakes.

You can find a description of Brake Assist (BAS) on or of BAS PLUS on.