Checking Brake Fluid Level and Leaks

Check the brake fluid level in the reservoir tank. It should be between the "MAX" and "MIN" lines on the reservoir tank.
If the brake fluid level is extremely low or below the "MIN" level, check the brake system for leaks.
Release the parking brake lever and check that the brake warning lamp goes off. If not, check the brake system for leaks.

Fig 1: Checking Brake Fluid Level And Leaks
Courtesy of NISSAN MOTOR CO., U.S.A.