Elecshock5

I'm getting a P0740 check engine code, which is a TCC circuit malfunction. The automatic transmission fluid level is fine, but i'm getting very poor shifts with some power loss at higher rpms (3000+). It seems that it does this more when the engine is cold, but begins to function better as it approaches normal operating temperature. I've heard that replacing the tcc solenoid will fix this, but i'm a little reluctant to begin without more solid proof of what the real cause of this problem is, so I can keep it from happening again.