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Old 04-14-2019, 04:52 PM
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Default PO420 & Catalytic Converter question

I'm getting a PO420 code from my OBD. I have a Flowmaster exhaust, but the catalytic converters are OE on my 2005 Dodge Ram 1500 5.7. I'm probably going to replace both sides with Flowmaster catalytic converters (along with new bolts, etc.), but I'm unsure if I need to get an exhaust pipe flange gasket (donut) to mate the new pipe with the old exhaust manifold. I'm pretty sure I do, just never done that before. Any advice? Any recommendations on Walker versus Felpro, etc.?
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Old 04-14-2019, 05:16 PM
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Have you used a infrared temperature gun to check the O2 sensors ?
The output should be about 100 degrees Fahrenheit hotter when the engine is fully warmed up.

Read more at: https://www.obd-codes.com/p0420
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Old 04-14-2019, 05:43 PM
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Thanks, GT - I'll check it out. Thanks for the link too. I'm picking up a IR Temp Gun today and will post my results later, probably next week.

Last edited by Lorisfarmer; 04-15-2019 at 06:49 AM.
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Old 04-28-2019, 07:10 AM
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Quote:
Originally Posted by GTyankee View Post
Have you used a infrared temperature gun to check the O2 sensors ?
The output should be about 100 degrees Fahrenheit hotter when the engine is fully warmed up.

Read more at: https://www.obd-codes.com/p0420
I finally was able to check temps up stream and down stream on both sides when the truck was fully warmed up:

Upstream driver side: 425 degrees
Downstream driver side: 543 degrees

Upstream passenger side: 499 degrees
Downstream passenger side: 590 degrees

I'm still getting the PO420 code. I do have a Magna Flow catback on the truck, if that makes any difference.

Any thoughts?
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Old 04-28-2019, 08:24 AM
Marley Marley is offline
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When I got the p0420 code , I replaced both downstream 02 sensors and used the adapters, code never came back.
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Old 04-28-2019, 09:02 AM
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Quote:
Originally Posted by Marley View Post
When I got the p0420 code , I replaced both downstream 02 sensors and used the adapters, code never came back.
I understand about the sensors, but what are the adapters you mentioned? Thanks for the reply!
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Old 04-28-2019, 11:46 AM
Marley Marley is offline
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Quote:
Originally Posted by Lorisfarmer View Post
Quote:
Originally Posted by Marley View Post
When I got the p0420 code , I replaced both downstream 02 sensors and used the adapters, code never came back.
I understand about the sensors, but what are the adapters you mentioned? Thanks for the reply!
You can use sparkplug non foulers "42002" as I did and drill them out with 1/2" bit, you'll need a vice or order part specific off Amazon, more expensive but ready to install.
This is done to fool the ECU by showing a variance between upstream and downstream cats.
We have no emission inspections here.
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Old 04-28-2019, 04:57 PM
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Quote:
Originally Posted by Marley View Post
You can use sparkplug non foulers "42002" as I did and drill them out with 1/2" bit, you'll need a vice or order part specific off Amazon, more expensive but ready to install.
This is done to fool the ECU by showing a variance between upstream and downstream cats.
We have no emission inspections here.
LOL - no inspections here in SC either! Thanks a lot for the tip!

An edit: Do I need one of these on each of the four sensors? Or just on the sensor that's throwing the code (Bank 1 upstream)? I found them for cheap on eBay.

Last edited by Lorisfarmer; 04-28-2019 at 05:17 PM.
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Old 04-28-2019, 08:00 PM
Marley Marley is offline
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The extensions only need to be on downstream 02 sensors......replace the upstream with NTK as needed.
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Old 04-29-2019, 06:25 AM
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Will do. Thanks.
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