I have a 1998 (I think) hx head on a ex block in a Si. It started throwing a code for the Primary o2 sensor heater (code 41). I started to look for a new 5-wire and while in the process, the car started running like ****. It would spit and sputter and idle erratically. I bought a different uce (p2n) thinking that maybe the ecu was bad, but that new one did nothing for it. I put an ex (p2p) in it that I had laying around and it ran good enough to get it home.

I bought a new o2 sensor and put it in. I also installed the newer hx ecu (p2n-A034) into it and everything was working good. Recently (after my kid took his amp out of it) it started throwing a code 91, fuel tank pressure sensor. I switch the gas cap with my 04 civic lx to see if that was the problem, but it wasn't. This morning I decided to throw in my original hx ecu (p2n-A022) to see if the code 91 reappears. As soon as I started the car after installing the ecu, I get a code 41 (primary o2 sensor heater).

WTF, two different ecu's, two different codes. This is driving me f*in crazy.