Level Check

WARNING: This page is about a different car, the 2003 Nissan Murano. However, it is still accessible from the selected car via links, so may be relevant.

Make sure the fluid level in the sub tank is within the standard (between MAX and MIN lines).
Visually check around the reservoir tank and sub tank for fluid leakage.
If fluid level is excessively low, check brake system for fluid leakage.
If brake warning lamp remains illuminated after parking lever is released, check brake system for fluid leaks.

Fig 1: Identifying Brake Fluid Level Check Points

Courtesy of NISSAN MOTOR CO., U.S.A.