2021 BMW 540i xDrive Brake Fluid Level Warning Indicator Switch Replacement Cost

It is vital that the brake fluid reservoir is always full since a low brake fluid reservoir can let air into the brake master cylinder and brake lines. Not only would that render the brakes less effective, it would cause the need for a brake system flush and bleed. To prevent this situation, a brake fluid level switch is attached to the brake fluid reservoir, and illuminates the brake fluid level warning light when the brake fluid level becomes lower than acceptable.

The brake fluid level warning indicator switch is situated on the exterior of the brake fluid reservoir, but extends to the inside of the reservoir as well. This is a simple switch that is actuated by any conductive liquid, so when the brake fluid is not in contact with the switch, the brake level warning light is activated. Once the brake fluid level in the brake fluid reservoir is returned to normal, the illuminated brake warning indicator will turn off, given that the parking brake is not on and there are no errors in the system.

If the brake level sensor were to fail, you may notice the brakes feel spongy, but the brake warning indicator is not illuminated. This would be the case if the brake fluid became too low, but the faulty brake fluid level switch did not alert the driver. Also, the brake fluid level warning indicator would illuminate when there is plenty of fluid in the reservoir. In some vehicles, the brake fluid warning light may prevent the vehicle from moving out of 'Park'.

Unless the vehicle's brakes have been affected by low brake fluid, the vehicle is generally safe to drive. If the vehicle will not shift from 'Park', the shift-interlock override switch can be used to operate the gear selector. However, when the brakes feel too soft and spongy, the vehicle should be repaired on site or towed to a certified repair facility before operating.