Cat replacement

I have a 2014 Chevy Cruze 120k miles I changed the Cat but the PO420 code on my scan tool came lean bank 1 but it comes up 2 time before changing my front cat it come up 3 times on my scan tool trying to figure out what is the problem. The front cat is from Walker. Need some help on what I should do

So what did you get? a dog :laughing:

Seriously,you need to get that fixed by a pro.

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So the P0420 is NOT a P0420 but a P0171?? And you had this code BEFORE you changed the cat and after? If so, you have another problem likely not related to the cat to fix. If I’d seen a P0420 and a P0171 at the same time, I’d have changed the O2 sensors first since they share the list of causes for both codes. But your P0420 went away, so it is most likely a vacuum leak.

The most common causes of a P0171 is…

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There have been THOUSANDS of cats replaced over the years when the actual problem was the O2 sensors. Midas and a few other national chains paid heavy fines in multiple states for doing that.


The P0420 code was there before can came back on 6 days after replacing convertor

Take it to a knowledgable mechanic, who will properly diagnose the issue instead of throwing parts at it. Just because a code has a certain part name in the description, doesn’t mean that part is the problem.

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It’d be pretty unusual for a 2014 model year car to need a catalytic converter. In fact… I believe most exhaust system parts are covered by the factory warranty for 8 years, so you may have paid for this new one needlessly.

Agree with taking it to a mechanic.


This is why you should never go straight from a scanned code to a diagnosis. The code tells you that a reading is out of normal, not why it is out of normal.

You probably never needed a catalytic converter in the first place. You might have a malfunctioning oxygen sensor or two. Or you could have a bad air/fuel mixture due to some other problem like a malfunctioning mass airflow sensor. Or maybe your spark plugs are fouled, leading to an increase of unburned fuel in your exhaust.

My advice on what to do: Take this car to a qualified mechanic who will use your code as a starting point to reach a diagnosis, not the finishing point.

Throwing parts at a problem can be the most expensive way to fix it.


Only the catalytic converter is covered for 8years/80,000 miles in the exhaust system.

Under federal law, the catalytic converter and engine-control module are covered for eight years or 80,000 miles . Some other emissions parts carry shorter federal warranties, usually two years or 24,000 miles.


Test the entire exhaust system for leaks, including at the exhaust manifold/engine interface.

The original poster really needs to explain things a lot better. The actual number codes read before that cat replacement, the codes seen after replacement. The P0420 is the only one expressly posted. Any others were just mentioned as descriptions. I guessed a P0171 but no confirmation given. It is unclear when these occured. Finally, just who diagnosed and then replaced the cat? The OP?

If you are a professor, @professord14_176559 , I’d grade your post a C-


I’m not a professor nor do I know anything about cars that is why I posted in the community board to find out what steps I should take that’s all. As far as the description I reference back that I have zero knowledge about cars so I gave as much description that my scan tool had showed me yes it wasn’t a expensive scan tool either because not a mechanic. Just wanted answer and information on what to do from people who have more knowledge in the field than myself. Yes the problem is fixed

That’s great, glad your problem is fixed. Thanks for posting back. It would help future forum members a LOT if you posted the solution to your problem as well.

We don’t expect you know much about cars. We know posters can’t think of every significant data point. That’s why we ask questions about your post. It is up to you to answer those questions as best you can. If you don’t understand the question; say so. We can’t help you if you don’t help us understand.