P0420 code problem

8816 Views 3 Replies 3 Participants Last post by billym81, Nov 26, 2017

billym81

Discussion Starter · Nov 25, 2017

Hello, I brought an 2011 cruze last month and it had the check engine light on which turned out to be the P0420 code. They said they replaced the rear 02 that day, but the light came back on two days later. Took it back to the dealership to which they said I needed an new cat which they replaced. the light came back on a day later, this time they changed the rear 02 on Wednesday, got about 30 miles and the light came back on.
I notice two of the times the light came back on i was sitting at a traffic light waiting for to turn. What else would be causing this problem so I can finally get this fixed.

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Robby

· #2 · Nov 25, 2017

There really are no other 'What Else' from a part failure standpoint. Most likely will end up being a wiring or ECM problem.
Just get it back to the shop and let them tear their hair out.......kinda sucks for you but sometimes these things take a lot of time to figure out.
Once at the shop, avoid the urge to call and bug them about how soon it'll be done......it stops/slows the process of diagnostics.

Report back please.

Rob

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Izaacg816

· #3 · Nov 25, 2017

I had a P0420 briefly ... I noticed zero loss in power just the worry of a possible issue. Inspected 02 sensors and wiring and had no issues. I have a code reader and cleared the code. I also pulled the batterys negative post and let it sit 20 mins or so. I have not had the P0420 return. I got the code at 100k or so ... im at 123k now.

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billym81

Discussion Starter · #4 · Nov 26, 2017

I have a code reader as well, which is how I know what the code is. I have cleared the code a couple of times now before and after getting new 02 and cat. it seems to come back a day or two days later. I have not took the negative battery cable off yet

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