I know that code 43 is for the fuel system. My P06 w/v-tec was throwing that code, but how the hell does the ecu read the fuel system?? Is it through the O2 sensor? Because a problem with the fuel system can mean several different things (fuel pump, fuel filter, injectors ect) and obviously ECU's don't read those problems. So does anyone know how it works? Today I changed my fuel filter because I haven't done it since I owned the car and my car was bogging a little, so I changed the cap and rotor and that helped, but it still bogged. And every once and a while my CEL came on, but as soon as I shut the car off the CEL would go off. So today luckely I was driving to my tuner and the CEL went on. Code 43, so not knowing exactly what to do we changed the one thing that hasn't been done to the car and that was the fuel filter. Car seems to running good now, but wtf is up with code 43?

 

I believe it's a general catch-all code for when the existing measurements don't add up but none of the specific sensors is obviously completely gone.

Say your fuel pressure is low...
The ECU doesn't measure fuel pressure, and there's no code for that. The ECU reads TPS, MAP, IAT, & all that, and sets the injector duty cycle. But the O2 sensor says he needs more fuel. The ECU 'knows' that it's not right, but at the same time the O2 sensor acts like it's working correctly.

 

Consider that code to mean the O2 sensor is reading an overly rich condition, the code got lost in translation somewhere along the lines, it really means there are "unburned oxides". Hit the basics first, plugs, air filter, dist rotor, check the FPR and it's vacum line.