Q: I have a 06 Infiniti M45. The service engine light came on. Got the codes of p0420 and p0430. Wondering if I need to replace both O2 sensors.

Hi there. When the codes P0420 and P0430 come up, usually the catalytic converter has failed, but before you determine if you need to replace the catalytic converter, consider checking the following:

• A damaged or failed oxygen sensor on the exhaust system
• Wiring damaged to an oxygen sensor
• Engine coolant temperature sensor is not working properly
• Leak in the exhaust system
• The oxygen sensors are having the same readings
• Spark timing is retarded
• Leaking fuel injector or high fuel pressure
• One or more cylinders are misfiring
• The engine oil is contaminated

If all of the areas above are met and working properly, then the catalytic converter would need replaced. The codes are on as the Oxygen sensors have picked up the activity of the catalytic converter is below threshold. If you need further assistance with your check engine light on, then seek out a professional, such as one from Your Mechanic, to help you.