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Threw a code po420. I had just cleared codes po178 and po179…

Customer Question
Threw a code po420...

Threw a code po420. I had just cleared codes po178 and po179 by putting a flex fuel replicator and clearing the codes. Now all the sudden po420. Could they be related?

Mechanic's Assistant: Has the vehicle turned into a gas hog? And how does it start -- same as usual?

Starts faster and smoother. Always been a gas hog 2002 suburban, but not excessively

Mechanic's Assistant: Are you fixing your Flex yourself? What have you tried so far?

I put a replicator into sensor plug to trick computer. Supposedly will run fine and not throw code as long as you do not use e85.

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

No flex sensor codes came back, so thought it was fixed but came up to red light stopped and ses light came on now reading po420 thanks

Submitted: 5 months ago.Category: Chevy
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Answered in 4 minutes by:
11/16/2017
Chevy Mechanic: Pete, Auto Service Technician replied 5 months ago
Pete
Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 31,760
Experience: 14 years GM dealer Technician.
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Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

The P0420 code wont set in relation to the other codes you have.Here is a list of other codes you could have had that can cause the P0420 to set and the ones you had are not listed.

DTCs P0101-P0103, P0106-P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0131-P0135, P0137, P0138, P0140, P0141, P0151-P0155, P0157, P0158, P0160, P0161, P0171, P0172, P0174, P0175, P0200, P0300, P0325, P0327, P0335, 336, P0341-P0343, P0351-P0358, P0443, P0446, P0449, P0502, P0503, P0506, P0507, P1120, P1125, P1133, P1134, P1153, P1154, P1220, P1221, P1275, P1276, P1280, P1281, P1285, P1286, P1441, P1514, P1515, P1516, P1517, or P1518

This indicates that the three way catalytic converter is not operating properly.Check for any exhaust leaks or damage as well as for any after market exhaust components.If this is all o.k. then the three way catalytic converter system needs replaced to resolve this fault.In most cases it is the three way catalytic converter system needing replaced as I have seen and had to replace before in the past.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

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Customer reply replied 5 months ago
I do not have emissions test in my county, but are there any hazard in just running it with the code?
Customer reply replied 5 months ago
I have a very slight leak on passenger side exhaust manifold hardly detectable, but code was for bank 1 driver side where there is no leak
Chevy Mechanic: Pete, Auto Service Technician replied 5 months ago

I apologize for the delay.

Most likely the leak isnt causing this fault here.

If you have no emissions testing and it is running o.k. then you should be able to drive it.I do recommend at some point though to have it replaced.

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time,this can be done at any time and you can still come back here and reply if needed.Your 5 star rating is appreciated

Thanks Pete

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