Code 0420

2006 CHEVROLET HHR

86,000 MILES • 2.2L • 4 CYL • 2WD • AUTOMATIC

CHRIS CHUMLEY

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The 0420 code keeps throwing. I have replaced the catalytic converter and both 02 sensors. what can it be?

Nov 7, 2019 at 6:39 PM

KASEKENNY

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18,907 POSTS

I attached the diagnostic information that gives the detail about the other items to check. The largest cause of this (after the sensors and cat) is an exhaust leak. It could also be a wiring issue but check out the diagrams and let me know if you have questions. Thanks

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Nov 7, 2019 at 8:22 PM