so here's the thing I have a 00 Honda Civic auto good trans fluid no slips no hard shifts no noise but I got a p0740 code saying the torque converter solenoid/open any idea were should I start

 

Do you have a wiring diagram and multi meter?
If so check for continuity from ECU to torque converter solenoid, check for continuity on the return signal wire back to the ecu. Make sure it it getting the correct voltage to the sensor. If you have a scan tool with dealer level capabilities do an actuation test on the solenoid. Check the solenoid for proper resistance. Make sure all connectors are in good working condition with no corrosion on the pins. If everything above checks out then replace the TCM which I believe is part of the ecu so you could just swap it out with a known good unit.