p0300 code

Hey guys, new to the forum and have a question about a 04 Aveo. I have two codes showing up on my girlfrieds aveo, p0300 and soemthing 2105, i think it was U2105. I know the first one has something to do with the tranny. Any help or suggestions on where the problem lies is greatly appreciated. Many thanks.

P0300 is random misfire. It is an engine code.
U2105 is not in my book. Are you sure of that number ?

what kind of scanner you using?