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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I changed catalytic converter on a 2003 impala 3800 about

Customer Question

Customer: I changed catalytic converter on a 2003 impala 3800 about 6mths ago. Now the check engine light comes on again. Giving the code 420. Would it be one of the oxygen sensors? ***** ***** P.
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Submitted: 1 year ago.
Category: Chevy
Expert:  Gary replied 1 year ago.

this could be one of the )2 sensors if one was reading wrong

but when these set a 420 code the front of cat and rear of cat O2 sensors are matching readings and that is why the computer is setting the code

was this a direct fit cat converter you installed ?