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Code P0420, Catalyst System Efficiency Below Threshold Bank 1?

Tiny
DAVEM16
  • MEMBER
  • 2011 GMC ACADIA
  • 3.6L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 122,031 MILES
Hello,

My SUV listed above is an SLT model and has been losing power while driving on the freeway and it idles a little rough, sometimes. The engine light came on and I got a code that reads P0420: Catalyst System Efficiency Below Threshold Bank 1.
catalyst converter or-oxygen sensors? I've Googled it but I'm not sure what to do, is it a bad catalytic converter or oxygen sensors? I'm not a mechanic but I can do minor jobs and I haven't been working so I cannot take it to a shop. I saw online that they have bolts on cat converters, if that’s the problem. Is that something that I can do at home, is it easy enough? Do you have any blueprints on how to change them out and where the bolts are or if it the o2 sensors can you tell me where they are? I guess I’m looking for good advice from someone who knows. Please let me know if you need any more info.

Thank you for all your help, I truly appreciate it.
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Sunday, June 25th, 2023 AT 11:08 AM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,961 POSTS
Sure, this is a common problem, I wouldn't bother with the oxygen sensors because the catalytic converter is bad and can cause the low power as well as it plugs the exhaust system because the catalytic has come apart and blocks the outlet. Here is a video of the job being done to help you fix the problem, you can get the part from the dealer for about $900.00 to $1,300. It is the entire header pipe and cats.

https://youtu.be/CORe9JyrexI

Please let us know if you need anything else to get the problem fixed.
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Sunday, June 25th, 2023 AT 3:41 PM
Tiny
DAVEM16
  • MEMBER
  • 14 POSTS
Oh man, I was hoping it would've been a cheaper fix. How many converters does the Acadia have? I think I saw 3 on Google but I'm not sure, also do I change one or all, if it has more than 1. I'm asking because the code says Bank1. Thank you
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Monday, June 26th, 2023 AT 1:36 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,961 POSTS
My bad, on this car they do sell them separately, bank 1 is on the right side of the engine closest to the fire wall.

Catalytic Converter 15903506 $865.00

Here is how the job is done. Check out the images (below). Please let us know if you need anything else to get the problem fixed.
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Tuesday, June 27th, 2023 AT 9:20 AM

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