Check it out. I've researched this to death using the search, but I just want to see if I can get anymore possible solutions. I have a 96 civic ex coupe. That has been throwing code P0172 (System Too Rich Bank 1) I had already changed the spark plugs, air filter, , distributor cap and rotor, fuel filter, and I checked the resistance in the spark plug wires and they are ok . I just changed the primary o2 sensor, and in addition to getting p0172, I'm also getting p0170 Fuel Trim Malfunction (bank no. 1). What else could be the problem?