Nissan Repair: engine coolant temperature cicuit malfunction, mass air flow sensor, mass air flow

Question
120k, nissan maxima 95. code P0115, it's hard to start and easy to stop. temp scale looks normal. what's the issue? and what's the function of this circuit?

Answer
P0115
Diagnostic Trouble Code P0115 indicates a problem with the fuel management system on the right cylinder bank. The right bank is also called the rear bank. It is cylinders 1,3,5.

The Front Heated Oxygen Sensor for the right bank sent signals to the Engine Control Module indicating an excessively lean fuel mixture. The ECM attempted to correct this problem by directing the fuel injectors to supply more gasoline. Further signals from the Oxygen Sensor indicate that the attempt to correct the lean mixture condition was unsuccessful, and the fuel mixture continues to be too lean.

Possible causes include ...
- Intake air leaks
- Defective Front Heated Oxygen Sensor
- Fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Faulty Mass Air Flow Sensor