My '01 Pathfinder "Service Engine Soon" light came on. This happened when it was under warranty and they ended up replacing a bad O2 sensor. So, the O2 sensor is what I immediately suspected. I went to the local Advance Auto and they put a code reader on it. It read P0158 and P0160. The guy told me that this was for an O2 sensor. He looked it up and it's $288. I did a Google search on both the codes and it pulled up a page that had both codes listed next to TSB 01-045A.
http://www.alldata.com/TSB/76/99760110.html
I'd like to know what this TSB says because it may be related to the problem that I'm having. I also saw another TSB 02-007A that I'm interested in as well. Is there any way to get a copy of these TSB's without paying for them? Also, is there any way to verify exactly what codes P0158 and P0160 mean?

Finally, my wife put 89 octane gas in the last time she filled up. Could this cause the "Service Engine Soon" light to come on and for those codes to come up?