Code questions: 1140/1145, 0158, and 0420

[thad-01PF]

AutoZone read codes P1140, 1145, 0420, and 0158 on my 2001 Pathfinder LE today after I had looked at the SES light for a while. I've read a bit on the 1140/1145 codes, but not much on the other two.

How difficult are these issues to repair? I'm not a crack mechanic, but I can usually figure out what to do with adequate instruction as long as the task isn't too invasive or complex. These would be totally new areas for me, but I'm willing to give it a shot if it's simple enough.

Thanks in advance. For the record, I'm at 88,000 miles and this is my first engine issue of any kind.

[thad-01PF]

Bumping this up to try one more time...

[timmack]

zerothread/174934 < read that thread. the 1140/1145 is easy to fix, granted you can turn a ratchet and unplug a connector.