The computer is telling you a cylinder is not firing. The computer should also tell you what cylinder. It probably is not fuel related. When the engine is misfiring, the light should blink. A misfire will cause excessive gas to be dumped in exhaust causing the O2 senser code. The extra gas will also destroy the cat and then you will start picking up codes from the rear O2 sensor. You are going to have to check coils, wiring and things in that line. A bad plug, wire, coil, corroded terminal or shorted wiring will cause the plug not to fire. You should have individual injectors for each cylinder, so you can rule out throttle body.