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 InspectionAir Intake Actuator Inspection [Manual Air Conditioner]
1. Connect battery positive voltage to air intake actuator terminal B (or C),
connect terminal C (or B) to ground, and then verify that the air intake actuator
operates as shown in the table.
If the operation condition is not normal, replace the air intake actuator.
...
Transaxle Oil Replacement [G35 M R]
1. Park the vehicle on level ground.
2. Remove the aerodynamic under cover No.2..
3. Remove the drain plug and washer.
4. Drain the oil into a suitable container.
5. Install a new washer and the drain plug.
Tightening torque
39—59 N·m {4.0—6.0 kgf·m, 29—43 ft·lbf}
...
Recommended Oil
U.S.A., Canada, and Puerto Rico
Use SAE 0W-20 engine oil.
Mazda Genuine Oil is used in your
Mazda vehicle. Mazda Genuine 0W-20
Oil is required to achieve optimum fuel
economy.
For maintenance service, Mazda
recommends Mazda Genuine Parts and
Castrol ® (U.S.A. only).
Only use SAE 0W ...