Level Check

WARNING: This page is about a different car, the 2013 Nissan Armada. However, it is still accessible from the selected car via links, so may be relevant.

Make sure the fluid level in reservoir tank is between MAX and MIN lines as shown below.
Visually check around reservoir tank for fluid leaks.
If fluid level is excessively low, check brake system for leaks.
If brake warning lamp remains illuminated after parking brake pedal is released, check brake system for fluid leaks.

Fig 1: Identifying Brake Fluid Level (MAX Or MIN)
Courtesy of NISSAN NORTH AMERICA, INC.