Edit: Crap, ignore the below, thanks Lou. I just figured out you have a manual transmission. Someone just replaced your PCM (computer) with a replacement that is programmed for an automatic. It won't cause any problems other than the constant P0743. You can ignore it or replace the PCM with one meant for a manual transmission.
The TCC circuit is what locks up the torque converter that sits in front of the transmission. It uses a solenoid to lock it up which is powered by 12 volts. The solenoid receives a constant 12 volts on one side. When the PCM (computer) decides the torque converter should be locked, it applies a ground connection to the other side of the solenoid which then locks the torque converter to eliminate its normal slippage.
This shows the TCC, it's on the very left. Constant 12 volts to it from Fuse 11. The PCM provides a ground on the other side of the TCC Solenoid at the bottom. Very simple circuit to troubleshoot with nothing more than a cheap meter or 12 volt test light if you know anything about electrical circuits. The TCC solenoid operates much like a light bulb... give it power and ground connections and it works.
View attachment 227895