Check engine codes
 

I have a 93 s10 blazer 4wd. I only recently bought the truck and I just checked the codes that it was giving me and I got 28, 43, and 45. I looked them up and it looks like 45 is just an o2 sensor. 28 is transmission range pressure switch and 43 is a knock sensor error. I was wondering if anyone knows more about what these mean and what steps I can take to fix them.