Check Engine Light Came On on 2003 Suzuki Aerio

My check engine light came on. Stopped at Advance Auto. They hooked up to a hand held computer. The reading was: torque converter. What is that? The light went out on its own before my mechanic could see it.

Asked by for the 2003 Suzuki Aerio
it is part of the transmission. the code number would really help.