# Code P0420



## markmashley (Mar 20, 2018)

P0420

This is a permanent code cannot be cleared with code reader.
Will only clear if system decides problem no longer exists.

I used CRC Intake valve cleaner as directed after one week I re-scanned problem has now gone away.

My conclusion is that dirty valves were causing said code.


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## Ma v e n (Oct 8, 2018)

P0420 is not that type of code. It is able to be cleared with a scan tool.

It's possible dirty valves could lead to poor running which could poison a cat. But it's not likely. I haven't seen any notably filthy LE2 intake valvetrains yet. Not have I seen an instance where a spray in intake cleaner cured a truly failed cat. It was more likely a fuel related issue that time resolved.


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## markmashley (Mar 20, 2018)

Ma v e n said:


> P0420 is not that type of code. It is able to be cleared with a scan tool.
> 
> It's possible dirty valves could lead to poor running which could poison a cat. But it's not likely. I haven't seen any notably filthy LE2 intake valvetrains yet. Not have I seen an instance where a spray in intake cleaner cured a truly failed cat. It was more likely a fuel related issue that time resolved.


Ok, that's interesting my bluedriver scan tool indicated it was a permanent code?

You might well be right regarding the fuel, I had just ran some Redline SI 1 complete fuel system cleaner through it and the code threw up shortly afterwards, any thoughts as to why?

So, the little Cruze egr/valvecover does a pretty good job of "catching" those nasty oils after all. What kind of buildup and at what mileages approx have you observed the valves?


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## Blasirl (Mar 31, 2015)

:moved: This is a service issue and not a tutorial - moved from Gen II Engine/Trans Tutorials to Gen II Service Issues


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