Dreaded P0420 Code :( (1 Viewer)

[CarolinaGX]

As the title suggests, I got the P0420 code (Catalyst System Efficiency Below Threshold Bank 1) after filling up on my way home from wheeling in TN . While wheeling, I had some hits and caused a leak at the joint between the 2 cats on the driver's side (bank 1). The next day it went out so i thought nothing of it and I replaced the gasket along with a new stud then tightened it all down eliminating the leak. The code came back and keeps coming back after 20 miles or so. Could this be a coincidence? I ordered a new downstream O2 that will arrive tomorrow but I am not sure if this will be the fix or if I will be spending my birthday/bumper $$ on a new manifold/cat. Thoughts?

 

[GXO]

Sensor will probably fix it.

 

[CarolinaGX]

fingers crossed!

 

[CarolinaGX]

I replaced the down stream O2 sensor on the driver's side and the code came back. I guess my next step is to replace the upstream O2 sensor. If that doesnt work I will either graft a new cat on the manifold or go big and do the whole exhaust but that is not my preferred route.

 

[GXer04]

If the sensor doesn’t work switch to a Remflex gasket. It will take up the irregularities of the pipe for a proper seal. Did the trick for me a couple years ago.

 

[CarolinaGX]

GXer04: which gasket are you referring to?

 

[GXer04]

Remflex 6006 Exhaust Collector Gasket for Mopar, (Set of 2) Amazon product ASIN B00B2HMFJ4
I believe it was this one. Check that the ID matches.

 

[intoodeep1113]

You can also put in a O2 spacer for about $8 that will make the light go away.

 

[Brake Weight]

I replaced the down stream O2 sensor on the driver's side and the code came back. I guess my next step is to replace the upstream O2 sensor. If that doesnt work I will either graft a new cat on the manifold or go big and do the whole exhaust but that is not my preferred route.

I would take a gander at your cat itself. I'm willing to guess the honeycomb inside got busted up.

p0420
"....This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs)….."

P0420 Catalyst System Efficiency Below Threshold

How to diagnose, repair, and info on symptoms and causes of a P0420 engine code which means the catalytic converter is no longer performing at a normal level.

www.obd-codes.com

 

[CarolinaGX]

I replaced the upstream O2 sensor and tightened an unknown bolt on the back of the head right by the wire of the O2 and after 500 miles, no more lights!!!! The Upstream O2 was $119 for the Denso sensor on Amazon. When I get the P0430 code (passenger side) I will just replace both sensors on that side but I am glad I did one at a time for this one to identify the issue. I hope this helps someone else.

 

[CarolinaGX]

Darn it, it came back!

 

[nadroj]

fought this one off and on for 3 months on our 08

at first i would just clear the code and it would come back a week or two later. then replaced both post cat 02 sensors. the code was gonefor about a month and popped its ugly head up along with a very sooty exhaust. replaced the pre cat air fuel sensors and we have been code free for 3 months.


just my experience

 

[CarolinaGX]

I did both sensors on the driver side and it went away for 1000 miles or so. Now it is back, i cleared the code, and it came back quickly. I might do the passenger sensor as I think Dan mentioned that the system compares both banks to each other.

 

[GXO]

If you replace all of the sensors and it is still happening...may be cat/manifold time.

 

[GXO]

Can also be coilpacks and plugs too...if you have a plug/pack going out it can read rich post cat with older cats. A full PM job usually clears these up. Can't just replace sensors if she isn't running right!

 

[Brake Weight]

I would take a gander at your cat itself. I'm willing to guess the honeycomb inside got busted up.

p0420
"....This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs)….."

P0420 Catalyst System Efficiency Below Threshold

How to diagnose, repair, and info on symptoms and causes of a P0420 engine code which means the catalytic converter is no longer performing at a normal level.

www.obd-codes.com

If you replace all of the sensors and it is still happening...may be cat/manifold time.

This. Did you do any off-roading that may have lead to an impact on one or both cats? Any water crossings that could have contacted cat(s)? I was getting this code on my Tacoma and when I finally pulled the exhaust, the cat was melted looking all around the outside of the honeycomb. I’m guessing 16 hour runs across TX hammering down i20 at TX speeds lead to this.

 

[kbahus]

O2 sensor spacers are the answer as mentioned earlier. No reason to make this harder or more expensive than it is.

 

[CarolinaGX]

The truck runs great. There are no hickups at all. It pulls strong, idles smoothly, and is getting good MPG's.

 

[runningdrew]

The truck runs great. There are no hickups at all. It pulls strong, idles smoothly, and is getting good MPG's.

after replacing all the sensors?

 

[CarolinaGX]

No, i only replaced the upstream and downstream on the driver's side. I havent done anything on the passenger side yet.

This all started after wheeling for 3 days. I never hit the cat's because they are so tucked into the frame but i did hit the exhaust enough to cause a leak at the joint after the second cat on the driver's side. I replaced the gasket and there is no more leak. We drove 500-700 miles with the light off, then it showed up the other day out of the blue.