Level Check

WARNING: This page is about a different car, the 2008 Infiniti FX45 and 2008 Infiniti FX35. However, it is still accessible from the selected car via links, so may be relevant.

Make sure the fluid level in reservoir tank is within the standard (between MAX and MIN lines).
Visually check around reservoir tank for fluid leakage.
If fluid level is excessively low, check brake system for leakage.
Release parking brake pedal and see if brake warning lamp goes off. If not, check brake system for fluid leakage.

Fig 1: Checking Fluid Level

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