I had transmission fluid leak that I ultimately traced to a loose hose going into the radiator a couple of weeks after I got the car. I added fluid to the trans, and all seemed well. About a month later I get a transmission service required message. I took it to my friendly neighborhood AutoZone to get the codes and there were 2 - P0740 was the first one and P1618 (I think) was the second. Could running low on fluid have caused this? The transmission does not slip and still shifts smoothly, but I have this "check engine" light I need to get rid of. I just want to understand what could be the root cause first.