Operational Check
WARNING: This page is about a different car, the 2003 Infiniti QX4 and 2002 Infiniti QX4. However, it is still accessible from the selected car via links, so may be relevant.
With engine off, depress brake pedal several times until pedal height no longer changes. Press and hold brake pedal down. Start engine. If pedal goes down slightly, power brake unit is okay. If pedal does not move, check for air leak.