1. Disconnect the brake fluid level sensor connector from the master cylinder.
2. Inspect for continuity according to fluid level between the brake fluid level sensor terminals.

If not as indicated in the table, replace the reserve tank.

Brake Switch InspectionSaving Fuel and Protection of the
Environment
How you operate your Mazda determines
how far it will travel on a tank of fuel. Use
these suggestions to help save fuel and
reduce CO2.
Avoid long warm-ups. Once the engine
runs smoothly, begin driving.
Avoid fast starts.
Drive at lower speeds.
Anticipate when to apply the brakes
(a ...
Manual Transaxle Removal/Installation [G35 M R]
CAUTION:
Secure the steering wheel using tape or a cable to prevent the steering shaft
from rotating after disconnecting the steering shaft. If the steering wheel
rotates after the steering shaft and the steering gear and linkage are disconnected,
the internal parts of the clock spr ...
Electric Power Steering Oil Pump Component Disassembly/Assembly
CAUTION:
The internal parts of the EHPAS control module and motor could be damaged
if they receive an impact. Be careful when handling the EHPAS control module
and motor to prevent the component from getting hit. Replace the electric power
steering oil pump component if it has recei ...