Hey guys!

I got a pretty common P0420 code and just recently put a brand new catalytic converter and 2 new oxygen sensors on it. It got rid of the check engine light for about 2 days, but then the same code came back on. I think there is another Cat farther down the exhaust pipe, but I'm not sure if that's the best next step.

Have any of you guys had the same issue? What should I fix next??

Welcome to the forum.
First, what year, engine and mileage do you have.
Assuming it's a 1.4, is the new cat a GMgenuine? It is the only cat that works for the GM 1.4t engine.
P0420 is a discrepecy between o2s1 and o2s2 as seen by ecu. If a new cat is not able to clean up exhaust to keep computer happy then the engine has an issue and is sending raw fuel, oil or coolant through exhaust, reducing efficiency to below acceptable range.
Repair engine issue and cat will return to acceptable range and code will stay cleared. 420 doesnt always mean bad cat. But If original was destroyed or clogged/burnt, then replacement was needed.

 

I got a 2013 with about 140k miles on it. The engine is a 1.4t I'm pretty sure. I know it has a turbo on it.

Shoot. I got a cat off of ebay. It was like $65 and the GM one I found was like $800!!

 

Aftermarket parts NEVER fix 0420.

Oem is the only way.

 

Just about every car on the market ACCEPT the Chevy Cruze you can use an aftermarket cat. You might be able to make it work (not bring the CEL back) by putting a spacer in with the downstream O2 sensor. Some cars need spacer elbows as well.

Just throwing that idea out there as a chance to make it work, not entirely sure you can return the cat once you put it into service. Don't even know if the spacer / elbow with make it work just an inexpensive idea.

 

You might be able to make it work (not bring the CEL back) by putting a spacer in with the downstream O2 sensor.

No. You can't make a bad cat work by putting a spacer on the rear sensor, the only thing that that can do is fool the diagnostic into a false pass.

@allecks : You bought an inert converter, the cost difference was because it doesn't have any platinum, palladium or rhodium in it. You know, the actual catalysts.

I'd make a play to get a refund on the grounds that the item was not as described. If it has no catalyst, it's not a catalytic converter.

What I can't figure out is why cats fail.

In a new converter the size of the precious metal particles is really small, and the surface area of the converter substrate is at its maxiumum. As the converter ages the particles slowly consolidate and the substrate surface area drops, both of which reduce converter efficiency.

Another thing that'll do it is high rates of misfire (rates that will cause the MIL to flash). I've got some chunks of melted converter brick at my desk from that, they never fail to impress.

 

Another thought:

What if I upgraded the exhaust to have a down pipe that doesn't have a cat? If I did that, there wouldn't be a cat. There has to a be a way people turn off that code if they don't even have a cat right?

I'm thinking that if I'm going to spend a grand on parts I might as well spend it on parts that will upgrade my car right? I just don't know what happens if you don't have a cat. Do you just have to live with the P0420 code for forever?

 

Another thought:

What if I upgraded the exhaust to have a down pipe that doesn't have a cat? If I did that, there wouldn't be a cat. There has to a be a way people turn off that code if they don't even have a cat right?

I'm thinking that if I'm going to spend a grand on parts I might as well spend it on parts that will upgrade my car right? I just don't know what happens if you don't have a cat. Do you just have to live with the P0420 code for forever?

The main point to consider is: is your original catalytic converter really no good? The reason p0420 triggers is because a malfunctioning engine sends way too much noxious exhaust through the cat and the cat cannot efficiently burn off all the noxious parts and send "cleansed" exhaust past the rear o2 sensor.
Your engine is what needs work. The original gm cat may still be useable if the exhaust from the engine is normal.

 

Officially it all depends on where you live. In the USA and a few other countries you must have a cat converter. For the US its a federal law that you have a cat even if you do not live in an area that does smog testing. If you live in an area that does emissions testing then you have to have a working cat and readiness status on all your sensors, having a tuner turn that code off probably will not pass emissions. Getting a tuner to turn off the code in the US might prove difficult as well.

Unofficially, its your car do what you want, we are all adults and are responsible for our own actions or inactions.

I can say that going the spacer route can help you pass emissions. My daughters old Eclipse had a falling cat and replacing the O2 sensor did not help. I had to install a spacer to get it to pass emissions. Even with that the code still came back but not until after it passed. I bit the bullet and replaced the cat on that car after than with no more issues.

 

Aftermarket parts are used refurbished parts. That means not up to oem specs.


There are 500M threads of using Aftermarket. I haven't seen one actually correct the problem yet.

What I can't figure out is why cats fail.

I junked my 94 grandam and 97 cavalier. At 250k miles and both had their original cat.

 

Hey guys!

I got a pretty common P0420 code and just recently put a brand new catalytic converter and 2 new oxygen sensors on it. It got rid of the check engine light for about 2 days, but then the same code came back on. I think there is another Cat farther down the exhaust pipe, but I'm not sure if that's the best next step.

Have any of you guys had the same issue? What should I fix next??

Hey guys!

I got a pretty common P0420 code and just recently put a brand new catalytic converter and 2 new oxygen sensors on it. It got rid of the check engine light for about 2 days, but then the same code came back on. I think there is another Cat farther down the exhaust pipe, but I'm not sure if that's the best next step.

Have any of you guys had the same issue? What should I fix next??

Did u have it replaced at a chevy dealership had the same problem they fixed it no issues!