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  1. #1
    Join Date
    Jan 2008
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    P0420... Oh.. Boy!

    Need some input from those that may have dealt with this before or know something that I may be overlooking. I am a little confused now.


    2007 JGC Limited 5.7 HEMI 114k miles (I know... Not an LX, however it has a HEMI and this is probably the best place for anything HEMI related)


    At about 2k rpm Bank one sensor one (Driver side up stream) cycling between .075v and .857v very rapidly while Bank one sensor two (Driver side down stream) was holding between .725v and .780v. Sounds about normal, right? Temp at the bank one Cat (Driver side) inlet was 468* and the outlet was 569*. A bit close but still ~100*. For a P0420 code I should have a wonky O2 sensor reading or no temp increase or even a decrease going through the Cat. If anything I may be running a bit rich on that side but nothing major.


    I think that everything checks out on that side and repeat the test on Bank two to see what is going on there for a comparison...


    Still 2k rpm Bank two sensor one (Passenger side up stream) cycling between .031v and .820v very rapidly while Bank two sensor two (Passenger side down stream) was holding between .685v and .725v. Still sounding normal, right? Temp at the bank two Cat (Passenger side) inlet 577* and the outlet 497*. Hmmm... That does not seem right, however no P0430 code.


    I repeat the test at idle with the following results


    Bank one sensor one cycling between .055v and .812v. Bank one sensor two holding between .760v and .780v. Bank one Cat inlet 337* and outlet 445*


    Bank two sensor one cycling between 0.072v and .793v. Bank two sensor two holding between .790v and .800v. Bank two Cat inlet 374* and outlet 399*


    So... Looks like all the O2s are good but my Bank 2 Cat is going out. Nothing pointing to a P0420 code and I do not have a P0430 code.

    What am I missing?

    Thanks in advance for any and all input!
    Gunner (Mike)
    2007 Tor-Red MSRT W/ SRT group I, II & III
    LMI true CAI, MMPG 87mm TB, GTP Ported Intake Manifold, Inertia Performance Heads, FRI Tomahawk, 176* T-Stat, SLP U/D pulley, JBA Long Tubes with catted mids, Custom cat-back W/ Blastin' Bob's, PT 2800, Blue tops, Getrag W/ 3.73s and CMR tuned by Brent at DTP.
    11/11/11 11.504 @ 118.00, 1.598 60' W/ 315/35/17 NT05R DRs @ 20lbs, 93 oct pump gas, 4125lbs, and a DA of -680

  2. #2
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    PO420....Was the engine smoking?
    Likes 1FST4DR, punisher69, KYUUBI liked this post



  3. #3
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    Maybe bad Cat(s)

  4. #4
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  5. #5
    Join Date
    Jan 2008
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    Update: I erased the code last night and went for a 20 minute joy ride. It did not come back as active or pending. Drove to work this morning, still no light, Code not active however it set as pending. Drove home made a couple of stops on the way, same thing. FYI about 30-45 minute trip to and from work most of it 45mph with several stop lights with about 10 minutes of 55-65mph sustained. Took a quick look/listen for exhaust leaks, nothing definitive. Most times I have heard a leak on the HEMIs it is pretty pronounced. It does seem to have a slight "HEMI tick" from the drivers side Valve cover.


    Thanks for the input guys.

    Quote Originally Posted by DBL.DWN View Post
    PO420....Was the engine smoking?
    It was a couple of days ago when I Seafoamed the Intake track... Looked like a Willy Nelson tour bus!

    Quote Originally Posted by 1FST4DR View Post
    Maybe bad Cat(s)
    The tests above point to the Bank two (Passenger side) being bad however there is no code set on that one. The Bank one tests good however that is the code that set.


    Yep...

    I will get it up on some ramps in the morning and get a good hands on look at the exhaust system. Based on other input I will be sure to check the Manifold bolts and all flanges and bring some wrenches with me. Checked the build sheet it was sold with Cali/NY emissions... So I don't have that going for me.
    Depending on how long this goes I may look into having it smoke checked... lol.
    Gunner (Mike)
    2007 Tor-Red MSRT W/ SRT group I, II & III
    LMI true CAI, MMPG 87mm TB, GTP Ported Intake Manifold, Inertia Performance Heads, FRI Tomahawk, 176* T-Stat, SLP U/D pulley, JBA Long Tubes with catted mids, Custom cat-back W/ Blastin' Bob's, PT 2800, Blue tops, Getrag W/ 3.73s and CMR tuned by Brent at DTP.
    11/11/11 11.504 @ 118.00, 1.598 60' W/ 315/35/17 NT05R DRs @ 20lbs, 93 oct pump gas, 4125lbs, and a DA of -680

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