SES 0420 ... Cat inefficiency - FirebirdV6.com/CamaroV6.com Message Board

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  • SES 0420 ... Cat inefficiency

    I recently put a 3" catco and a borla on my 2001 Firebird. After the usual 20 miles, the SES came on and is staying on. Autozone read the code as a 420 (i.e. cat inefficient ... rear O2 sensor). Are there any fixes? What is the PCM trying to do to compensate for this problem?

    Thanks
    Zaino; FireBatCave Decals; Red Inside<br /><br />K&N Filter & Lid; Removed MAF screen; FRA; Raised Air Box; 180°F Stat; BMR STB; 3\" Catco & S-pipe; Borla Cat-Back; O2 Sim; HPPIII; NGK TR55s; Taylor 8mm wires<br /><br /> <a href=\"http://www.cardomain.com/id/cbass300\" target=\"_blank\">http://www.cardomain.com/id/cbass300</a>

  • #2
    I have a similar setup and I don't have a SES light. Disconnect your negetive battery cable for 30 min then get under your car and make sure your sensor is pluged it good. Hook the negative battery cable back up and drive down the road @ 55 mph for about 2-5 miles. From what I read it resets the computer and recalibrates your fuel air ratio. I don't really know if its true, but mine works lol. Hope that helps you.
    1999 Firebird Black<br />A4 3.08 gears<br />Mods: Carbon Fiber Whisper Lid, Raised Air Box, K&N Air Filter, Direct Hits Ignition, Flowmaster American Thunder 3\", 160 Degree Hypertech Thermostat, SLP Fan Switch, 3\" High Flow Cat<br /><a href=\"http://www.cardomain.com/member_pages/view_page.pl?page_id=273903\" target=\"_blank\">My car on Cardomain</a>

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    • #3
      Looks like you might have to get an 02 sim.
      <b>99 Camaro Z28 A4</b><br />R.I.P. 00 Firebird 3.8<br />14.89 @ 90, 2.03 60\'

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      • #4
        All you guys have older cars. I don;t mean that in a negative way at all, but I think my car's programming is much tighter with minimum specs. I had troubl;e with a 160 stat too in which the engine never got up to temperature.

        Does anybody think the cat is failing because my engine is running colder due to larger pipes? (This was autozone's suggestion, not mine!)
        Zaino; FireBatCave Decals; Red Inside<br /><br />K&N Filter & Lid; Removed MAF screen; FRA; Raised Air Box; 180°F Stat; BMR STB; 3\" Catco & S-pipe; Borla Cat-Back; O2 Sim; HPPIII; NGK TR55s; Taylor 8mm wires<br /><br /> <a href=\"http://www.cardomain.com/id/cbass300\" target=\"_blank\">http://www.cardomain.com/id/cbass300</a>

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        • #5
          Do you have the slp fan switch? If you have a homemade fan switch you will throw a SES light.
          1999 Firebird Black<br />A4 3.08 gears<br />Mods: Carbon Fiber Whisper Lid, Raised Air Box, K&N Air Filter, Direct Hits Ignition, Flowmaster American Thunder 3\", 160 Degree Hypertech Thermostat, SLP Fan Switch, 3\" High Flow Cat<br /><a href=\"http://www.cardomain.com/member_pages/view_page.pl?page_id=273903\" target=\"_blank\">My car on Cardomain</a>

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          • #6
            Well on the newer v6s (2000 and up) they have an o2 sensor right behind the cat to montor how effecent the cat is running. On the newer car you have a 2 stage cat and all aftermarket cats are 1 stage. The 2 stage cat helps exhaust gases to heat up quicker when your car is running cold untill it gets up to temp. This helps reduce cold start emmsions. Now with the 1 stage cat you do not have that so the o2 sensor knows this thus setting off the SES light. You will have to ethier have the old cat put back on or get a o2 simulator. The best bet would be to have the old cat put back on. The newer cats flow pretty good compared to the old v6 cats(93 to 99).
            2004 Dodge Dakota 3.7 litres of raw power!!<br />Nothing but a 6!<br />Do you know for sure? John 3:18

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            • #7
              Good 'ol code 420! I had my catco on for quite a while and never threw the code. A couple months ago I threw the 420 code and it turned off within 3-4 days by itself...came back again a week or two later then went away...haven't seen it again until just the other day and its on right now. Don't worry about it. It comes and goes. From what I've heard (and can feel) the PCM doesn't do anything that will affect the performance while the light is on.

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