Ok I had no o2 sensor connected on my car for a while...so when I did a cel check I was getting code 01 and 41 for primary o2 and primary heated o2 sensor...that was the only code I was getting..so today I went and put the o2 sensor on and the check engine light went away...after driving for a while I now get the check engine light back on with code 01 for primary o2 sensor and now also I get code 23 knock sensor. I never even got knock sensor..the other funny thing is that sometimes the check engine light may go away while driving and then come back after a while...what could this be?...any ideas?

I have a B16a1 with a obd1 sohc vtec wire harness and a gsr obd-1 p72 ecu on a 94 civic ex...