pulled codes from my ecu

[95nismo240]

i have a 95 nissan 240sx and just had the engine rebuilt. then check engine light has always been on even before the rebuild and i only got about 200 miles to a tank of gas. i decided finally to pull the codes. the ecu threw out code 103 (Park/Neutral Position Switch). Code 111(Inhibitor Switch). and Code 125(Line Pressure S/V). i have no idea what this means!!!. i reset the ecu and drove about 5 miles and then the check engine light came on again. i still get bad gas milage even with the tune up and the rebuilt engine but i still havent changed my o2 sensors. tommorrow i am changing them hopefully. if anyone can tell me what these codes mean it will be appreciated.

[NISTECH]

they are all related to your trans. I would suggest checking the wiring for the harness coming off the trans. make sure all the connectoins are clean.