P0420 won’t go away

Martin Mechanic Washington Posted   Latest   Edited  
Unsolved
Driveability
2016 Chevrolet Trax LS 1.4L (B LUV) 6-spd (6T40)
P0420 — Catalyst System Efficiency Below Threshold Bank 1
Check Engine Light

So keep getting Cat code on this car, installed after market cat twice and both o2 sensors. Code came right back first drive cycle. Flex pipe had slight leak so replace that and checked pcm calibration is current. Code still returns. scan tool shows o2 sensors reading normal. All out of ideas 

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Andy Diagnostician
Indiana
Andy
 

How many miles are on this car? But the answer to the question you asked is in the first sentence. ‘Installed aftermarket cat twice’.

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Darren Technician
Wisconsin
Darren
 

Original equipment is necessary on a few models

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Jay Owner/Technician
Rhode Island
Jay
 

Had same issue on a 12 Chevy equinox same issue.

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Jay Owner/Technician
Rhode Island
Jay
 

Rear cat clogged ? I had same issue on 12 Chevy equinox and I put oem cat on and code never came back.

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Jamie Owner/Technician
Ontario
Jamie
 

Unfortunately you answered your own question. Aftermarket doesn't work in all situations. Send me a pm for a solution.

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Victor Technician
California
Victor
   

there is a bulletin specifically for premature wear on cats with DTC P0420 or P0430. It explains to check for poor crimps on the coil grounds to the engine block. Document ID is 4446449 within gm service info. This might not be your fix but it is worth verifying as you are experiencing that exact DTC. Also, did you perform the O2 sensor resistance relearn procedure?

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Stephen Owner/Technician
California
Stephen
 

OEM only for converters

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Mitchell Owner/Technician
Oregon
Mitchell
 

I ran into this on a California emission Cadillac, even though we replaced with California aftermarket catalyst, code still came back. OE only on some models.

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Justin Technician
California
Justin
 

Check and see if o2 sensor location were in same vicinity between aftermarket and oe what is in mode 6 data?

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Ronald Owner/Technician
California
Ronald
 

Your really need to put an OEM cat on this thing. At a minimum, the aftermarket cat should be CARB certified. California made the aftermarket cat makers really beef up their cats and test the heck out of them to prove they are up to the task. My go to is the CARB website aftermarket cat converter database. It tells you the approved cats for a given model, the engine family number(emissions level…

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Carey Technician
Indiana
Carey
 

The link ssl​.​arb​.​ca​.​gov/AftermarketPar…

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Jorge Mechanic
New York
Jorge
 

So many cars with aftermarket CATs. Once they installed OEM, gone. Lesson learn many times over.

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Richard Instructor
Florida
Richard
 

Oem only for cats and O2 sensors On these GMs.

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Mark Owner/Technician
Alabama
Mark
 

We already did this same thing and had to replace the aftermarket cat with an OEM cat ….. the aftermarket worked fine once it got up to temp and you could maintain above idle rpms, it would set the fault at low speeds because it would cool down & cause the P0420 fault to set

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Robert Technician
Michigan
Robert
   

TSB for 2016 Cruze & other 2016 GM premature cat damage and mystery p0420/430 check ignition coil grounds …..edit ; I see Victor post now

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Marco Owner/Technician
Indiana
Marco
   

Oem cat it’s the way to go, aftermarket cats don’t work on these. Another method is adding a secondary small carb aftermarket cat after your current one or installing two small carb cats in series, the flex pipe would have to be modified a bit but it works, my local muffler shop has done this a few times with success

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Jeff Owner/Technician
Arizona
Jeff
 

Absolutely requires an OE CAT. If you want an eye-opener, get your camera into the aftermarket CAT when you remove it and compare to the OE. There's a reason why its $1k more. Just be happy you're not replacing the CAT on a 2014-ish Honda with CA emissions…

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Danny Technician
California
Danny
 

You might want to listen to what Jim Kemper says about aftermarket catalytic converters on Matt Fanslow's Pod Cast. player​.​captivate​.​fm/episode/730aba…

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Thanks
Christopher Owner/Technician
Arizona
Christopher
 

Does it have a aftermarket air intake….ive had that be the culprit more than once…

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Tyler Technician
Kansas
Tyler
 

Been here, done this, got the T-shirt. OE only. Anything else is a waste of your time/money.

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Wayd Owner/Technician
Montana
Wayd
 

“installed after market cat”…..There's your problem right there.

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Andrew Diagnostician
Indiana
Andrew
 

1.4's on all platforms require OE cats. I have tried various different ones with no success. Even companies that claim “oe equivalent” . We only use factory here on these 1.4's, all Chrysler 3.6's, and any Nissan product. Obviously there are others than I am forgetting.

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