Help needed to identify bad cat or bad o2 sensor

[richey]

This is the first time I am using Forscan to diagnose my P0430 code (Catalyst System Efficiency Below Threshold (Bank 2). I just changed out my bank 2 downstream sensor a month ago with a Denso sensor. Based on the catalyst bank 2 reading it is obvious that it is reading too high, so possible a bad cat. However looking at oxygen sensor bank 2 sensor 1 the values are 0 vs the 10/23 values of bank 1 sensor 1. Is this actually an indication of a faulty bank 1 sensor 1?


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[t9087]

P0420 and P0430 are always bad cats.

 

[richey]

P0420 and P0430 are always bad cats.

You don't find it odd that bank 2 sensor 1 is reading zeros?

 

[t9087]

We have a lot of 16-19 PIUs in our fleet, and all of them have had the cats replaced (Bank 1or Bank 2) with those codes. Once we replace them those codes never come back till about the time they get wore out again from all the idling. We don’t read the data PIDs with P0420 or P0430 anymore.

The 0 readings could mean the car was in Open Loop at the time.

 

[ProjectSHO89]

You don't find it odd that bank 2 sensor 1 is reading zeros?

No. Zero is equal to the minimum which means it is within the parameter limits. Perhaps, at the moment of time that the Mode $06 data was read, the value hadn't been updated yet. Impossible to know. Since it was a failure, it's best to simply look past it.

As mentioned by others, these codes are almost always an bad converter.