P0421 Code Problem, Please Help - DodgeTalk : Dodge Car Forums, Dodge Truck Forums and Ram Forums

Closed Thread
Thread Tools
post #1 of 2 Old 05-06-2009, 01:20 PM Thread Starter
Registered User
Join Date: May 2009
Posts: 1
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
(Thread Starter)
Question P0421 Code Problem, Please Help

I have a 2001 dodge stratus coupe.

My check engine light will be on for days and then it will go off for a day and then come back on for days. So I have taken it to 3 shops and got the diagnostic test done on it 3 times. All 3 times they told me the code was a
P0421 (warm up cat efficency low bank 1)

The first shop wanted to replace the 02 censors front and back. They could not confirm to me that it would fix the problem for sure it was just one step and it could fix the problem but it might be something else. SO it seems like to me they were just guessing at what the problem was.

The second shop told me that it was the catalystic converter that needs to be replaced. So that was something different from the first place. So I wanted to get one more opinion.

The third shop read the test gave me the code and said that they have another team of course for more money that could actually pin point the exact problem. Now I was thinking why was this test not just done in the first place then.

I have a couple questions.

First is there really another test besides the diagnostic test that could pin point the exact problem of this p0421 code problem.

Second I have been told that not fixing this problem will not cause any damage to my car and that I will just not be able to pass an e-check. Is this true?

Third is there a way or a tool I can buy to turn my check engine light off so that I can just pass the e-check and deal with the problem later if I needed too?

Thank you in advance for any help with my problem.
Matt23 is offline  
Quick Reply
Sponsored Links
post #2 of 2 Old 05-07-2009, 01:23 PM
Registered User
hemimech's Avatar
Join Date: Aug 2007
Posts: 358
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Most likely the catalyst material has deteriorated. To set the 0421 fault both upstream and downstream O2 sensors have to be indicating the same reading for a set of seven samples of 12 seconds each during warm up. To me this indicates that the O2’s are probably good & that they are working equivalent to one another. Typically with a good catalyst the upstream O2 will be reading the rich/ lean thing back & forth rather quickly. Meanwhile the downstream should be nice and stable in the middle ground indicating a functional catalyst. So if the O2 signals follow each other too closely then the catalyst is no longer effective & a fault is set. It won’t hurt the engine but it’s probably not going to pass the emission test.
hemimech is offline  
Closed Thread

Quick Reply

Register Now

In order to be able to use most of our features, you must first register.
Please enter your desired User Name, your Email Address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
The registration process requires you to activate your membership by following a link in an E-Mail that will be sent to you immediately upon completing this form. You must enter a valid email address or you will not receive this activation code and you will NOT be registered. Your E-Mail address is NOT publicly available to anyone as policy.

AOL E-MAIL USERS: Please click HERE for important info pertaining to your e-mail address.

Email Address:


  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
    User Tag List

    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page

    Forum Jump

    Similar Threads
    Thread Thread Starter Forum Replies Last Post
    Error code p0421 voldog 2G Dodge Stratus - General Talk 0 12-26-2006 04:29 PM
    Problem with Code mocho 2G Dodge RAM - General Talk 2 03-26-2006 09:14 PM
    95 neon code 43 problem t_taulbee Dodge Neon - General Talk 1 05-05-2005 06:33 PM
    Problem code baseball401 1G Dodge Durango General Talk 2 04-16-2005 11:56 PM
    Please help........Problem Code manueljlg 3G Dodge RAM - General Talk 3 08-12-2003 10:44 PM

    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off

    For the best viewing experience please update your browser to Google Chrome