Fluid Level Sensor Inspection

Disconnect the sensor connector.
Connect an ohmmeter to the connector.
Starting with the fluid level above MIN, verify that there is no continuity.
Remove the brake fluid and verify that there is continuity when the level is below MIN.
- If not as specified, replace the sensor.
Fig 1: Fluid Level Sensor Continuity Table & Connector View
Courtesy of MAZDA MOTORS CORP.