Why does TC Lockup not occur in overdrive?

What is your question?

There are no dashboard warning lights, No negative scan codes in history or otherwise. While driving, scanner shows shift progression 1st through 4th including a lockup signal without faults however, lockup does not occur. This is not intermittent but continuous. no other symptom other than higher RPMs and poor FE. Could this be as simple as a seized Lockup control solenoid which is not showing a fault code? Thank you