Checking Brake Fluid Level and Leaks

WARNING: This page is about a different car, the 2005 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.

Check the brake fluid level in the sub tank. It should be between the "MAX" and "MIN" lines on the sub tank.
Visually check around the reservoir tank and sub tank for leaks.
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
Courtesy of NISSAN MOTOR CO., U.S.A.