Originally Posted by nookie
I thing the consensus is once you get the P20EE - The damage (to the CAT) is done, it will keep coming back indefinitely until cat replaced.
To prevent P20EE = latest flash (only helpful if never seen P20EE).
I think that's true if the Cat was the issue. If a clogged DEF system was the issue, there is a chance the Cat is still ok.
P20EE means the Cat isn't operating within it rated efficiency. If it's too lean on DEF, you get too much NOx and a P20EE. A bad Cat has the same result. After the DEF system is fixed, an further P20EE codes are probably indicating a bad Cat.
Of course none of use know for sure. This is all deduced from my experience and reading all the other sequences of codes, failures, and repairs reported on here. Collectively, I think we may have a better grasp on this than many of the service techs.
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