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P0420 code related to heat shield?

  #1  
Old 03-07-2018, 02:48 PM
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Default P0420 code related to heat shield?

I have a 2006 Accord coupe EX (2.4) with 175 K miles. Bought used and Carfax shows no cat replacement, solid maintenance records. BUT looks like the dealer put in an aftermarket converter (Walker EPA Ultra Direct Fit). Car runs fine -- no hiccups or egg / exhaust smell.

The CEL is now on and I get a P0420 code (only that code). The CEL light occasionally goes off but comes on again after a few miles. I haven't tried Cataclean or any "quick fix" yet, but really don't want to replace the cat. (It passed MA inspection the day before the CEL light came on, so I have some time to fix or try the sensor hack.)

When I look at the cat it looks like the heat shield has a gap in it (pics attached). My main question is whether the heat shield gap might be triggering the cat error code. Also welcome any suggestions / thoughts folks have and whether the aftermarket cat is likely the CEL / 0420 trigger.
 
Attached Thumbnails P0420 code related to heat shield?-cat-converter.jpg   P0420 code related to heat shield?-cat-2.jpg  

Last edited by snowman; 03-07-2018 at 03:32 PM. Reason: error in original post
  #2  
Old 03-07-2018, 03:18 PM
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The heat shield wouldn't affect the cat efficiency. P0420 is usually the catalytic converter or an exhaust leak.
 
  #3  
Old 03-08-2018, 08:52 PM
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Are you sure the shield is not touching the wire that connects to the O2 sensor?
It kind of looks like it from the picture

Looks like the wire might be rubbing and maybe it is bare and shorting out? Just look at the wires and see if the insulation on the wires is bare...
 
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Old 03-08-2018, 09:03 PM
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Originally Posted by rockhoundrob View Post
Are you sure the shield is not touching the wire that connects to the O2 sensor?
It kind of looks like it from the picture

Looks like the wire might be rubbing and maybe it is bare and shorting out? Just look at the wires and see if the insulation on the wires is bare...
Even if the wiring was faulty, P0420 would not be the only trouble code, there would be another code like P0137, P0138, or P0141. Without those other code(s) present, it is likely the cat or an exhaust leak.
 
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Old 03-09-2018, 05:10 PM
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Originally Posted by redbull-1 View Post
Even if the wiring was faulty, P0420 would not be the only trouble code, there would be another code like P0137, P0138, or P0141. Without those other code(s) present, it is likely the cat or an exhaust leak.
Agreed. The last time I had a code P0420 code, it was from a bad cat. I thought it was either the cat or the sensor, since it could be either. But, I was doing some exhaust work to the car, so I changed the cat first. It fixed the CEL light.
 
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