Automatic wont shift past 2nd

[Lopin18]

A friend of mine bought a transmission from me, the old one broke because the car doesnt shifts to 3rd, and when starting on D it doesnt launches right, has to use L to start moving ok, so i sold mine to him, and the problem still is there!

I wanna help him out, where can i start? I asked for ECU model code to check if its the wrong ecu, but after that i dont have any idea, what might it be???? Support will be appreciated i wanna help a fella 240sx lover

[Rucca]

Is he still using the same torque converter?

[ken240sx]

torque converter...start checking signals from all transmission sensors...other than that swap the ecu out with a known working one.

[4wheeldrifts13]

Torque Converter.. I had the same problem until 5spd conversion