Help...what are these trouble codes?

I have a 95 Altima SE and the check engine light stays on. I checked the codes and got the following:

3 longer 4 short flashes
7 longer 7 short flashes

3 long flashes, 4 short flashes is a code 0304-Knock sensor. And 7 long, 7 short, is a code 0707 which is the rear O2 sensor. Inspect the harness and connectors visually. If they are connected and you don't see any harness damage try replacing the O2 sensor and clear the codes to see if the code 0304 resets.