Nope. You're interpreting those codes incorrectly. Diagnostic fault codes never ever say to replace a part or that one is bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. When a sensor or other part is referenced in a fault code, it is actually the cause of that code about half of the time. First we have to rule out wiring and mechanical problems associated with that part, or, as in this case, look for what they might have in common.
The first step is we need to know the exact fault code numbers. There are over two dozen codes related to oxygen sensors, and they mean very different things. The same is true for the EGR system. It takes a properly-working sensor to report a defective condition. It's that condition we need to know, then we can figure out where to start the diagnosis.
The catalytic converter's efficiency is calculated by comparing the rich / lean switching rates of the oxygen sensors in front of and behind that converter. That means it takes two properly-working oxygen sensors to determine when there's a problem with the catalytic converter. If a defect is detected with either O2 sensor circuit, all tests on the catalytic converter are suspended since valid readings aren't available. It is also possible to detect a problem first with the catalytic converter, then that code is in memory when an O2 sensor defect is detected later. Here too we have to know which fault code was set so we can figure out what type of defect we're diagnosing.
Once you know the fault code numbers, you can start by looking at this list of definitions:
https://www.2carpros.com/trouble_codes/obd2/p0400
We can help with explaining what it takes to set those codes.
Aug 18, 2020 at 12:24 PM
