Notices
X-Type ( X400 ) 2001 - 2009
Sponsored by:
Sponsored by:

P0420 Code Question

 
  #1  
Old 07-22-2018, 09:37 PM
Junior Member
Thread Starter
Join Date: Jul 2018
Location: RI
Posts: 24
Thanks: 0
Thanked 2 Times in 2 Posts
Default P0420 Code Question

A couple of weeks ago the MIL lit up. When I checked the code it was a P0133 (O2 sensor, Bank 1). I replaced the O2 sensor, but now I have an intermittent P0420 code. Does anyone know if the two are related and if there is something causing it other than the worst possible located Bank 1 catalytic converter?
 
  #2  
Old 07-22-2018, 10:20 PM
Dr dome's Avatar
Senior Member
Join Date: Mar 2013
Location: Hellertown,pa
Posts: 613
Thanked 119 Times in 113 Posts
Default

Yes sometimes you need to replace both o2 sensors on that bank one. If it comes back you have 2 options
1 buy a new cat or a used one
2 buy o2 sensor extenders(not legal)

let me know if you need a used one

thanks,
The Dr
 
  #3  
Old 07-23-2018, 08:00 AM
iownme's Avatar
Veteran Member
Join Date: May 2011
Location: Upstate NY
Posts: 1,411
Thanked 121 Times in 109 Posts
Default

kitty wants a joint
 
  #4  
Old 07-23-2018, 08:23 AM
Junior Member
Thread Starter
Join Date: Jul 2018
Location: RI
Posts: 24
Thanks: 0
Thanked 2 Times in 2 Posts
Default

Thanks. I have a downstream sensor on order. The new upstream was a no name brand. Seems to be working fine, but I’ve read that the cheap ones can be squirrely. Could that be the cause?
 
  #5  
Old 08-10-2018, 10:57 AM
Junior Member
Thread Starter
Join Date: Jul 2018
Location: RI
Posts: 24
Thanks: 0
Thanked 2 Times in 2 Posts
Default

Update: the light went off then back on again. I tried to change the downstream O2 sensor, but couldn’t get it to budge, despite using two different O2 sockets. Will have a mechanic break it loose as soon as I have a chance.
 
  #6  
Old 08-10-2018, 12:48 PM
dwclapp's Avatar
Senior Member
Join Date: Oct 2007
Location: Houston, TX
Posts: 808
Thanked 269 Times in 228 Posts
Default

xjagRI: When an O2 sensor won't budge, an alternative is to cut the wires close to the sensor and use a deep 6 point socket, which grips the sensor better than the slotted sensor socket.
 
  #7  
Old 08-10-2018, 02:39 PM
Veteran Member
Join Date: May 2009
Location: Yorkshire, England
Posts: 23,011
Thanked 3,374 Times in 2,991 Posts
Default

+1
exactly what I needed to do
 
  #8  
Old 08-13-2018, 03:34 PM
Junior Member
Thread Starter
Join Date: Jul 2018
Location: RI
Posts: 24
Thanks: 0
Thanked 2 Times in 2 Posts
Default

Good tip. I’ll see if I can maneuver on into that space before I cut the wires. It’s a tight spot.
 
  #9  
Old 08-13-2018, 04:48 PM
iownme's Avatar
Veteran Member
Join Date: May 2011
Location: Upstate NY
Posts: 1,411
Thanked 121 Times in 109 Posts
Default

remember to use a good penetrating spray the day before...something like PB Blaster....not wd40
 
  #10  
Old 08-13-2018, 05:32 PM
Senior Member
Join Date: May 2006
Location: connecticut
Posts: 750
Thanked 116 Times in 94 Posts
Default

are you sure the o2 sensor is bad did you test it

In your case, the P0420 code stands for “Catalyst System Efficiency Below Threshold (Bank 1).” When you receive a P0420 code it means your catalytic converter is not operating at maximum efficiency. Usually this means your catalytic converter needs to be replaced or there is a problem with your O2 (oxygen) sensors.
 
  #11  
Old 08-13-2018, 07:35 PM
Larry-Cleveland's Avatar
Senior Member
Join Date: Sep 2015
Location: Cleveland, Ohio
Posts: 259
Thanked 31 Times in 31 Posts
Default This worked for me

I had the same problem on my car. This is what I used.

Amazon Amazon

I think my problem was all bad threads on the pipes so I had to use them (cough cough) Ya that was the problem (cough caugh) bad threads...honest!
 
  #12  
Old 08-14-2018, 06:53 AM
iownme's Avatar
Veteran Member
Join Date: May 2011
Location: Upstate NY
Posts: 1,411
Thanked 121 Times in 109 Posts
Default

if its a cat issue.... there are several cat cleaners on the market such as cataclean.
according to reviews....they seem ro often work and ive seen some people remove the upstream o2 sensor, pour in seafoam. replace sensor and take a ride
 

Last edited by iownme; 08-14-2018 at 06:55 AM.
  #13  
Old 08-19-2018, 06:39 PM
Junior Member
Thread Starter
Join Date: Jul 2018
Location: RI
Posts: 24
Thanks: 0
Thanked 2 Times in 2 Posts
Default

Latest Update: MIL went off then on again, so I checked the codes again. This time I had a P0305 and P1316 in addition to the P0420. So here is what I think is happening:

1. I have a misfire on #5 that has been happening, but finally threw a code.
2. P0305 code caused the car to throw a P1316 code.
3. The intermittent #5 misfire caused the O2 upstream sensor to fail (changed last month) and then the cat to become contaminated to the point is not working well. Which caused the P0420 code.

Does that sound reasonable?

Since I bought the car I have smelled burning oil when it is stopped at a traffic light or at idle. I’m thinking I have a valve (cam) cover gasket failure that fouled the #5 plug at the heart of all this. Hopefully the cat is not too far gone that it can’t be saved.

Today I ordered new valve cover gaskets, coils, plugs, upper and lower intake gaskets. I won’t have time to do the work for a couple of weeks. Interested in what y’all think about my theory.
 
  #14  
Old 08-20-2018, 06:34 PM
Senior Member
Join Date: May 2006
Location: connecticut
Posts: 750
Thanked 116 Times in 94 Posts
Default

when was yhe last time the plugs where changed
 
  #15  
Old 08-20-2018, 08:29 PM
Junior Member
Thread Starter
Join Date: Jul 2018
Location: RI
Posts: 24
Thanks: 0
Thanked 2 Times in 2 Posts
Default

Not sure. I just bought it a few months ago.
 
  #16  
Old 08-21-2018, 08:29 AM
iownme's Avatar
Veteran Member
Join Date: May 2011
Location: Upstate NY
Posts: 1,411
Thanked 121 Times in 109 Posts
Default

seems a lot of us get a cyl 5 misfire...usually caused by a bad coil.
 

Last edited by iownme; 08-21-2018 at 08:37 AM.
  #17  
Old 08-21-2018, 09:51 AM
Veteran Member
Join Date: May 2011
Location: Waterford, MI
Posts: 1,134
Thanked 151 Times in 125 Posts
Default

Originally Posted by iownme View Post
seems a lot of us get a cyl 5 misfire...usually caused by a bad coil.
Or oil in the spark plug well.
 
  #18  
Old 08-21-2018, 10:36 AM
Join Date: Sep 2008
Location: Damon /Houston, Texas
Posts: 6,843
Thanked 1,675 Times in 1,114 Posts
Default

Originally Posted by xjagRI View Post
Latest Update: MIL went off then on again, so I checked the codes again. This time I had a P0305 and P1316 in addition to the P0420. So here is what I think is happening:

1. I have a misfire on #5 that has been happening, but finally threw a code.
2. P0305 code caused the car to throw a P1316 code.
3. The intermittent #5 misfire caused the O2 upstream sensor to fail (changed last month) and then the cat to become contaminated to the point is not working well. Which caused the P0420 code.

Does that sound reasonable?

Since I bought the car I have smelled burning oil when it is stopped at a traffic light or at idle. Iím thinking I have a valve (cam) cover gasket failure that fouled the #5 plug at the heart of all this. Hopefully the cat is not too far gone that it canít be saved.

Today I ordered new valve cover gaskets, coils, plugs, upper and lower intake gaskets. I wonít have time to do the work for a couple of weeks. Interested in what yíall think about my theory.
you also need the IMT orings(2) for the intake manifold tuning valves in the intake manifold. They are common vacuum leak sources
 
  #19  
Old 08-21-2018, 09:44 PM
Junior Member
Thread Starter
Join Date: Jul 2018
Location: RI
Posts: 24
Thanks: 0
Thanked 2 Times in 2 Posts
Default

Thanks, I replaced the IMT gaskets with the OEM green ones a month ago.
 
  #20  
Old 08-21-2018, 09:45 PM
Junior Member
Thread Starter
Join Date: Jul 2018
Location: RI
Posts: 24
Thanks: 0
Thanked 2 Times in 2 Posts
Default

clyons, I, too think I’ll find oil in the plug well. Will let you know.
 

Thread Tools
Search this Thread
Quick Reply: P0420 Code Question


Advertising
Featured Sponsors
Vendor Directory

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: