Torque Converter Clutch Solenoid Circuit ?

A friend of mine has a '00 2wd 4.0 AW4 ~ 180K and he called because his CEL went on, had it read and came up as the torque converter solenoid circuit. PO had a new or rebuilt trans put in a while ago, Jeep runs drives fine no shifting issues. He's just wondering why CEL went on, im sure theres a number of reasons but I figured it probably just had a glitch and threw the light since he says no issues shifting. Figured I'd ask around here to make sure its nothing we need to look into further. He's since had reset and its off now.