Most times when code P0742 pops up it is from the torque converter clutch coming apart and the debris clogs the solenoid and restricts flow. You could try replacing the solenoid but the problem will likely come back as the damage is done. Something you could check first is to drop the pan and remove the filter and cut it open. If you see a lot of find debris in the pan and or inside the filter and it is dark in color or there is lots of fine metal shavings you can pretty much count on replacing the trans.
