Code P0420?

Tiny
BLBLAZER701
  • MEMBER
  • 2014 GMC TERRAIN
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 91,000 MILES
Getting a p0420 code. Is there any way for a DIY'er to determine if it's the actual catalytic converter? And I've tried to look up the cost for the part and kind of all over the place. Can you tell me what an OEM replacement part would cost?
Friday, January 3rd, 2025 AT 1:20 PM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,067 POSTS
With no other codes chances are the catalytic converter is bad but, if you have a scanner the long and short fuel trims should be within ±10%.

The P0420 code on your 2014 GMC Terrain indicates a Catalyst System Efficiency Below Threshold (Bank 1).

I have seen catalytic cleaners work pretty well, but to do the job right you must remove the unit and have it chemically cleaned, which should be cheaper. Please go over this guide as well:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Here is the cost:

Catalytic Converter Front California 22794837 $850.00
Federal 20910567 $1025.00

Here is what it looks like. Check out the images (below). Let us know what you find.
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Friday, January 3rd, 2025 AT 6:24 PM

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