Help with Engine Light Codes

Hey guys, i need some help. A few weeks ago my engine light went on. When i checked the codes, it was for the knock sensor and speed sensor. I got it checked out and they said the parts were fine but that if the light goes on again, i should see the dealer. Then a few days ago the light went on again. This time, it was for the automatic transmission communications line, the knock sensor, and the vehicle speed sensor. What do you think is my problem? I dont want to take it in to the dealer cuz they charge 80 bux just to look at it. Anyone have any ideas? I'd really appreciate it, thanks.

I got the same problem but I didn't even go thru the cpu codes. I know that it is the oxygen sensor, and might be the speed sensor, later