On Board Diagnosis Logic
WARNING: This page is about a different car, the 2004 Infiniti I35. However, it is still accessible from the selected car via links, so may be relevant.
Engine coolant temperature has not risen enough to open the thermostat even though the engine has run long enough.
This is due to a leak in the seal or the thermostat open stuck.
Courtesy of NISSAN MOTOR CO., U.S.A.