Hi Elizabeth, I'm pleased to assist you. P0430 code on your 2004 Nissan 350Z means that the three-way catalytic converter is not working. P0300 can be caused by anything from old spark plugs to vacuum leaks to poor engine compression. Take note of what Spencer mentioned as it holds true. Check the Vehicle Emission Control Information sticker usually found underneath the hood to check if it matches the emission control specifications. Let me provide you with the link to the options we have for catalytic converters and order at discounted price while supplies last. I hope this was useful. Shop with pleasure at Carparts.com! https://www.carparts.com/search?q=catalytic_converter&vehicle[model]=350Z&vehicle[make]=Nissan&vehicle[year]=2004&can=CPGG4850_CSQA_20220818

If you're getting both of those codes your catalytic converter (one ot both) may be bad. Go get them tested at a muffler shop. Go test pipes if you need to, but youl have to do those yourself as removing the converters are "illegal" if your state has emissions you cannot remove them. They arent cheap,bl but there are cheaper aftermarket better options. Good luck!

Hi Tommy, I'm glad to assist you. The P0420 code signals a low catalyst system efficiency. This code suggests that the oxygen levels are below the desired threshold, which most often results from problems with your car's exhaust or fuel systems. We suggest consulting a mechanic so they can pinpoint what part you need to replace. I hope this helps, and we thank you for inquiring.

Hi Edis, thank you for reaching out. We are unable to answer this question accurately since we do not know what is wrong with your vehicle. Kindly check with a mechanic. Have a nice day.

Hi Dwayne, I'm glad to assist you. No. The pair of oxygen sensors come with both left and right downstream oxygen sensors. We also have the front/upstream sensor. Grab our low-price promo and click the link below to buy it today. Happy shopping! https://www.carparts.com/oxygen-sensor/drivewire/set-arbn960913?can=CPJE1043_CSQA_20230310 (downstream sensor pair) https://www.carparts.com/details/Nissan/Maxima/DriveWire/Oxygen_Sensor/2007/SE/6_Cyl_3-dot-5L/REPS960910.html?can=CPJE1043_CSQA_20230310 (upstream sensor, order two pieces)

Hi Benji, I'm pleased to assist you. The P0174 engine code indicates that there is an issue with the air/fuel ratio provided to your engine. There are several reasons for this code, like vacuum leaks due to damaged intake manifold gaskets or punctured vacuum and positive crankcase ventilation (PCV) hoses, malfunctioning mass airflow (MAF) sensor, and a clogged fuel filter. So it's best to take it to a mechanic to get a professional, real-time diagnosis to determine what part or parts need replacement. Feel free to contact us with the vehicle information so we can assist you in finding the part for your vehicle. Have a good one.