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2011 Chevy Equinox 2.4L P0420 Code


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So my check engine light came on and I was able to pull a code P0420 Catalyst system low efficiency. Now I know this could mean a bad cat, bad O2 sensor(s) or even a crack in the manifold. I have a 2011 Chevy Equinox 2.4L with a little over 80k on it. Does anyone know if there is a common fix for this? I was hoping it was a loose gas cap or something lol...But seems from looking online it can be a variety of things. 

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Yes it could be a variety of things and the right thing would be to have it diagnosed either at a repair shop or a dealer, unless you are able to run some test on the 02 and exhaust. The other thing to consider is if there are some warranty or added warranty items available on this vehicle. If you haven't already, get your car loaded into myChevy 

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 . You'll be able to see if there are any recalls and service items extended to 150k. Some of these GM vehicles have additional coverage added to them because of known issues and some include the catalytic converter, fuel pump, and also oil consumption which could trigger your code as well. :D

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  • 3 weeks later...

here are a number of things that could be causing this p0420 catalyst efficiency code. The most common thing is the catalytic converter itself is no longer functioning properly.
The other likely thing is the rear O2 (oxygen) sensor is no longer working properly. Other things could include exhaust leaks, damaged exhaust pipes, damaged O2 sensor wiring/connectors, plugged catalytic converter, etc.
The easiest thing to do first is a visual check of things. Visually inspect the exhaust system for leaks, check the catalytic converter for dents, holes, severe discoloration, and check for a rattle inside. If any of those syptoms are there, the converter likely needs replacement.
Then, visually inspect the downstream O2 sensor (behind the converter). Check for broken wires, obvious faults, etc. If all that checks out, you'll want to check the operation of the O2 sensor. To do that, you'll need access to a scan tool or oscilliscope. Check that the waveform is pretty steady. If the reading fluctuates then the sensor is likely bad and will need to be replaced.
Try this, turn the ignition key to the on position, (engine not running) and pull the fuse to your ECM for 30 seconds and then re-install it. Once re-installed, start the engine and let idle for 1 min and then go for a test drive.
If the engine stalls, let it. The ECM is relearning the sensors and engine, just restart it and after 1 min when the RPM drops. Go for a test drive and see if the service engine light comes back on and re-scan for the DTC codes and address the issues indicated by the DTC code.
 

Edited by MCT
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So we left Saturday on vacation and left the equinox at the dealer to check into the car efficiency code, oil consumption, occasional hard shift, and slow l/f tire leak. So we'll see, they have it for the week. I also dug up a letter from GM for an extended warranty on replacing the cat if needed.

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