https://www.honda-acura.net/forums/s...d.php?t=125370

So, it must be a DX/LX then if the cat was in the header. The problem he's facing I'm sure is that he now only has one bung for one O2 sensor. The DC header is only made for the OBD2 EXs because of the CAT being in the OEM header. If he used an EX header, he needs to either get an EX CAT or get another bung welded into a test pipe for the secondary O2 sensor.

I'm willing to bet that he didn't mount one of the O2 sensors and that's causing the code.

Also, because it's a DX/LX he will have to extend the wires for both O2 sensors.