I have a 2000 Honda civic ex A/T that keeps throwing a code p0740. I have flushed the transmission, I have cleaned and tested all transmission solinoids checked the ohms and functionality on all transmission solinoids. I have tested the connectivity between the torture converter solinoid and the ecu (it's good). I have swapped all solinoids from an identical transmission (with a cracked case). I even pulled the transmission again and swapped the torque converter. The code is being trown when I drive at about 55 mph for about 5 minutes. The transmission is not slipping but it will shift hard every once in a while. My question is is there any thing I am missing be for I deemed the transmisson is bad. Could it be a bad ECU. Is there anything else I should be checking? Or did I get a bad replacement transmission?

 

P0740 indicates a lock up fault, not necessarily a lock up solenoid fault. The torque converter is probably the real culprit.