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 InspectionOil Pressure Switch Removal/Installation [Fw6 A EL, Fw6 Ax EL]
WARNING:
A hot transaxle and ATF can cause severe burns. Turn off the engine and wait
until they are cool.
Always wear protective eye wear when using the air compressor. If the air
compressor is used, any particles of dirt or soiling could spatter and get into
the eyes.
...
Instrument Cluster Configuration (Using Read/Write Function)
NOTE:
When performing configuration, it is necessary to read the vehicle specification
information from the instrument cluster before replacing it. Connect the M-MDS
to the vehicle and perform vehicle identification before removing the instrument
cluster. The vehicle specification i ...
Seat Weight Sensor Calibration [Two Step Deployment Control System]
CAUTION:
If any of the following work is performed, perform the seat weight sensor
calibration using the M-MDS.
Replacement with a new seat weight sensor
Replacement with a new seat weight sensor control module
Replacement with new passenger-side seat pa ...