Getting the transmission out of "limp" mode doesn't require clearing the fault codes. The transmission will resume normal operation once the actual malfunction is resolved. The fault codes will still be "stored" in the ETC module, but the shift quality will return to normal.

Perhaps you're confusing the term "reset" with erasing the fault codes. The "reset" usually refers to re-setting the adaptation data. While sometimes helpful in diagnosing transmiission issues, adaptation data at the limit shouldn't put the transmission in limp mode. It sounds like you've still got a problem.

FWIW, have you checked to see if the transmision control module is contaminated with ATF? It's been known to happen.