Brake Fluid Level Switch

The brake fluid level switch is a reed-type switch that is mounted through the master cylinder reservoir. The reservoir uses a magnet incorporated into the float. The brake fluid level switch is hardwired to the BCM  through separate signal and return circuits and is grounded to a body ground through a separate circuit. The BCM  provides a reference voltage to the brake fluid level switch. When the brake fluid level is low, the float drops allowing the magnet to close the reed switch, pulling the reference voltage low. When the brake fluid level is high, the float lifts, releasing the switch contacts and removing the ground to the BCM  .