Brake Fluid Level Sensor Inspection

WARNING: This page is about a different car, the 2008 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.

Disconnect the brake fluid level sensor connector from the master cylinder.
Inspect for continuity according to fluid level between the brake fluid level sensor terminals.
- If not as indicated in Fig 1, replace the reserve tank.
  
  Fig 1: Brake Fluid Level Sensor Continuity Reference Chart
  Courtesy of MAZDA MOTORS CORP.
  
  Fig 2: Identifying Brake Fluid Level Sensor Connector Terminals
  Courtesy of MAZDA MOTORS CORP.