Q: 05 Nissan Frontier has a code of p1283 and p0420. Why are these codes stored?

Hi there. The code p0420 is present for the O2 sensor behind the catalytic converter has detected the air fuel ratio is not within the limits. The code p1283 is present for the air fuel ratio sensor is registering a lean mixture. Check the fuel injectors to see if any of them are not working. If the engine is lean, there could be a vacuum leak on the intake or the fuel pressure could be lower than normal. Also, check the mass air flow sensor (MAF) to see if its dirty. If the MAF is dirty, clean the sensor with electrical cleaner and recheck the conditions. In order to get the warning light off, disconnect the battery for 30 seconds and hook up the battery. This will clear the codes so you can test drive the vehicle. If you need further assistance with the engine light on, then seek out a professional, such as one from Your Mechanic, to help you.