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 InspectionEssential Information
Introduction
Be extremely careful and prevent injury to yourself and others or damage to your
vehicle when using this manual for inspection and maintenance.
If you are unsure about any procedure it describes, we strongly urge you to have
a reliable and qualified service shop perform the work ...
Cell Phones
Cell Phones Warning
WARNING
Please comply with the legal regulations concerning the use of communication
equipment in vehicles in your country:
Use of any electrical devices such as cell phones, computers, portable radios,
vehicle navigation or other devices by the driver while the vehicle ...
Manual Transaxle [C66 M R]
Purpose, Function
The MTX converts the drive force (speed, torque, rotation direction) input
from the engine according to the shift lever operation inside the vehicle.
Construction
Operation
...