CEL after installing catback
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This is a discussion on CEL after installing catback within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; I've been running with a Helix non-catted downpipe, stock catback, and a Vishnu uppipe for several months. I got a ...

  1. #1
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    Question CEL after installing catback

    I've been running with a Helix non-catted downpipe, stock catback, and a Vishnu uppipe for several months. I got a CEL at first but used spark plug anti-foulers to extend the o2 sensor out of the exhaust flow and it fixed it.

    Last week I installed an Espelir JGT500 exhaust. This afternoon while driving to work I got a CEL while on the highway and it's still there. Hopefully it's just the rear o2 sensor. I'm thinking that maybe the flow of the straight through muffler is too much for the mechanical fix.

    So on to try the resistor fix. I've read that a 1 megaohm (or is it 1 megawatt?) resistor can be soldered into one of the wires on the o2 sensor. I've never bought a resistor before and I'm kind of clueless on how to do it. Assuming I go to Radioshack, do I just walk in their and say, "Hi, can I have a 1 Megaohm resistor?" Also which wire do I splice it in?
    - Steve -
    black 05 wagon/shaved emblems/25% tint/no drl/2.2k
    XPT stage 2/no silencer/K&N filter/Vishnu up/Helix dp/Espelir JGT500 catback
    05 STi 6mt/ACT street clutch/STi short shifter/black Prodrive knob/Group N tranny mount/auto ds/3.90 r160
    sedan rear sway/17x7 gold OZ Superleggeras/black stockers

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  3. #2
    Registered User scubee's Avatar
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    Quote Originally Posted by 240kph
    I've been running with a Helix non-catted downpipe, stock catback, and a Vishnu uppipe for several months. I got a CEL at first but used spark plug anti-foulers to extend the o2 sensor out of the exhaust flow and it fixed it.

    Last week I installed an Espelir JGT500 exhaust. This afternoon while driving to work I got a CEL while on the highway and it's still there. Hopefully it's just the rear o2 sensor. I'm thinking that maybe the flow of the straight through muffler is too much for the mechanical fix.

    So on to try the resistor fix. I've read that a 1 megaohm (or is it 1 megawatt?) resistor can be soldered into one of the wires on the o2 sensor. I've never bought a resistor before and I'm kind of clueless on how to do it. Assuming I go to Radioshack, do I just walk in their and say, "Hi, can I have a 1 Megaohm resistor?" Also which wire do I splice it in?

    I just installed my TBE and I used the Pony express MIL eliminator and it has work wonderfully for me. Hope you can get an easy fix though.
    Other car's I had:
    93' Camaro Z28, 95' Eclipse GS, 92' Integra GS, 91' MR2 Turbo, 00' Civic SI, 89' CRX SI, 97' Accord EX V6 (Totalled), 97' Wrangler 4x4, 91' Talon TSI AWD (Blown motor), 96' 240sx KA-Turbo, 96' 300ZX TT, 05' WRX, 05' STI (Totalled), 05' STI, and 92' SC400
    Still in the Family: 05' STI (Wife's Car), 92' SC400.

  4. #3
    Registered User bmxdave's Avatar
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    Your best bet is to go to Autozone or an equivelent and get the code checked out, its most likely a catalytic converter inefficiency code. Get an AccessPort and all your problems are solved.
    Mods - Perrin Uppipe, Crucial Racing Downpipe, SPT/Bosal Catback, Samco IC Hoses, Cobb Stage 2, K&N Panel, GPMoto Intake Elbow.

    www.negativesource.com

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    Banned JDM 3SGTE's Avatar
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    i have the same turboback as you do, and i have a helix uppipe. i started getting cel's on the highway while i was cruising, and it turned out to be the uppipe o2 sensor. did the 2.2ohm 1/2 watt resistor mod and it hasnt come back since. does the vishnu uppipe have a o2 bung and is yours still hooked up?

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    Registered User EtherealWRX's Avatar
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    some people get CEL's some dont, its really random IMO. Friend of mine went helix UP/DP comepletely catless no CEL's, running 20k miles. I had the Crucial UP and DP and my CEL came on like 3 months later. It's random really. Just my 2 cents.
    Have a Greddy Evo 2 cat-back Exhaust system, willing to trade for: Greddy Ti, Apex'I N1, or Apex;I GT cat-backs. California only! PM if interested!

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    Quote Originally Posted by JDM 3SGTE
    does the vishnu uppipe have a o2 bung and is yours still hooked up?
    Yes.
    - Steve -
    black 05 wagon/shaved emblems/25% tint/no drl/2.2k
    XPT stage 2/no silencer/K&N filter/Vishnu up/Helix dp/Espelir JGT500 catback
    05 STi 6mt/ACT street clutch/STi short shifter/black Prodrive knob/Group N tranny mount/auto ds/3.90 r160
    sedan rear sway/17x7 gold OZ Superleggeras/black stockers

  8. #7
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    I just went to Autozone and had the codes pulled .

    P0546 Exhaust gas temperature sensor circult high input

    So, I'm going to try this fix - 2.2K Ohm Resistor Mod

    I probably won't get to it till tonight or tommorow if at all depending on the rain we're having but I'll let you know if it works. It just seems odd to me that it would only start after I installed a catback. I've been running for about 10k miles with the uppipe in, then about 6k with the downpipe in.
    - Steve -
    black 05 wagon/shaved emblems/25% tint/no drl/2.2k
    XPT stage 2/no silencer/K&N filter/Vishnu up/Helix dp/Espelir JGT500 catback
    05 STi 6mt/ACT street clutch/STi short shifter/black Prodrive knob/Group N tranny mount/auto ds/3.90 r160
    sedan rear sway/17x7 gold OZ Superleggeras/black stockers

  9. #8
    Banned JDM 3SGTE's Avatar
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    yup, sounded just like me. took me a while to get the cel, and it happened while i was cruising in 5th on the freeway. its the uppipe. the resistor will work.

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    Radioshack was out of them, I'll try again tommorow.
    - Steve -
    black 05 wagon/shaved emblems/25% tint/no drl/2.2k
    XPT stage 2/no silencer/K&N filter/Vishnu up/Helix dp/Espelir JGT500 catback
    05 STi 6mt/ACT street clutch/STi short shifter/black Prodrive knob/Group N tranny mount/auto ds/3.90 r160
    sedan rear sway/17x7 gold OZ Superleggeras/black stockers

  11. #10
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    Thumbs up It Worked

    I put the resistor in. I cut about half the wire off of each side of the resistor so it wasn't sticking out in the air. Hope that doesn't make it fall out or anything. I started it up and the CEL was still on, but it cleared after I reset the ECU. I then simulated the conditions when it first came on (wide open around 100-110 uphill then coast downhill on the highway) and nothing yet. I think it worked, I'll post up if the light comes back on. Thanks for your help, guys.

    On a side note, I'm loving this catback (Espelir JGT500). I used to fly a Cessna 172 and it sounds almost the same on the highway. I'm not kidding.
    - Steve -
    black 05 wagon/shaved emblems/25% tint/no drl/2.2k
    XPT stage 2/no silencer/K&N filter/Vishnu up/Helix dp/Espelir JGT500 catback
    05 STi 6mt/ACT street clutch/STi short shifter/black Prodrive knob/Group N tranny mount/auto ds/3.90 r160
    sedan rear sway/17x7 gold OZ Superleggeras/black stockers

  12. #11
    Registered User Wade-0's Avatar
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    Quote Originally Posted by JDM 3SGTE
    i have the same turboback as you do, and i have a helix uppipe. i started getting cel's on the highway while i was cruising, and it turned out to be the uppipe o2 sensor. did the 2.2ohm 1/2 watt resistor mod and it hasnt come back since. does the vishnu uppipe have a o2 bung and is yours still hooked up?
    The sensor in the factory uppipe is for EGT, not O2. The bung on aftermarket uppipes is also for EGT, but it's a horrible place to monitor EGT.

    As for the rear O2 sensor MIL eliminator, you can get the schematics to make one yourself at wrxhackers.com. It's more than just a resistor. I have one that I made that you can try if you want to Steve, I didn't need it since my EcuTek reflash ignores those CELs.

  13. #12
    Registered User Sick Boy's Avatar
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    Quote Originally Posted by Wade-0
    The sensor in the factory uppipe is for EGT, not O2. The bung on aftermarket uppipes is also for EGT, but it's a horrible place to monitor EGT.

    As for the rear O2 sensor MIL eliminator, you can get the schematics to make one yourself at wrxhackers.com. It's more than just a resistor. I have one that I made that you can try if you want to Steve, I didn't need it since my EcuTek reflash ignores those CELs.
    Interesting. Question for you Wade-O. The bung is to monitor the EGT. I ordered a Helix catless up-pipe that has an EGT bung. I'm assuming I install the sensor there and I'm done. However, will this throw a CEL?

    A reflash is in the future after the exhaust, turbo, etc, are upgraded which will make this moot. But before that happens, I'd like to be CEL free.
    2004 Sedan Stage IV (w/ .5L envy) >>> Stripped & Sold!
    2007 Wagon Stock >>> Soon to be traded in for an 08 STI

  14. #13
    Registered User Wade-0's Avatar
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    Quote Originally Posted by Sick Boy
    Interesting. Question for you Wade-O. The bung is to monitor the EGT. I ordered a Helix catless up-pipe that has an EGT bung. I'm assuming I install the sensor there and I'm done. However, will this throw a CEL?
    It shouldn't throw a CEL, however the factory EGT sensor has a tendency to disintegrate when it's installed in a catless uppipe. It usually takes several thousand miles, but it can happen. I would recommend just getting the right size bolt and plug the hole, and use the 2.2K resistor fix instead. The factory EGT is only located there because of the cat, so it's an unneccessary risk to take if your uppipe is catless.

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