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Thread: P0420 with Cortex 91 Rotofab, magnaflow cats, new O2s, extenders

  1. 08-24-2015, 11:26 PM #1
    J Wikoff
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    Default P0420 with Cortex 91 Rotofab, magnaflow cats, new O2s, extenders

    My car popped this code today. I've had magnaflow cats in for a year or so. When I originally put them in, I also put in Denso upstream sensors. They started throwing intermittant codes a few months later. It was a minor annoyance until this spring when they got more frequent and P0420 started showing up too. So a few/several weeks ago I put in new ACDelco upstream sensors, extenders on the rear, and one new ACDelco rear sensor because it was crossthreaded from the factory and would not go back in. I'm running the Cortex 91 Rotofab tune and of course a Rotofab intake. The current tank is full of 91 ethanol free gas. Sometimes it's got 93 e10 in it. It was code free since then until today.

    Thoughts? If one or both of the cats were bad, would the extenders mask it? Or only to a certain degree, and if they are bad enough, extenders can't hide it anymore?
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  2. 08-26-2015, 09:44 AM #2
    J Wikoff
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    Bump.
    09 G8 GT SRM Premium Sport Sunroof



    HSV GTS Triple Gauge Pod, GXP Rear Sway Bar and Diffuser, HSV SuperSport Steering wheel, SOLO axle-backs, Magnaflow cats, Red Hot Shift Knob, Auto-dim Mirror, Hood Vent Mod, Removed Intake Cover, Rotofab CAI, Cortex, Infinity door speakers, MTX Re-Q5, Pioneer Amp & RF Sub, LED lows & fogs, Spyder tails, Power Slot rotors, Wagner Thermoquiet pads, Chrome lug covers, Glovebox light,

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  3. 08-26-2015, 10:55 AM #3
    Chewy
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    I'm guessing you read this:http://www.obd-codes.com/p0420

    That's all I have!

    2009.5 MSM GXP 500ish N/A RWHP. Mods include but aren't limited to: Texas Speed 418 (6.8L) fully forged held together with ARP from top to bottom, PRC 255cc heads, Rick Crawford intake plenum, TB port, polish and tune, Roto-Fab 102mm CAI w/LS7 MAF, Kooks 1-7/8" headers wrapped with DEI, Corsa catless system, Circle D 3200 Stall, 3.45 final drive, BMR's complete street bushing kit and sway bars, Eibach Pro Kit, G-Force Axles, running on staggered VMR 710's with Bridgestone RE11 rubber. HSV triple gauge pack with Calais smokers kit mod, V6 tails, debadge/rebadge, V6 door handles, AU black door trim, Maverick Man under hood strut covers, & washer and bolt kit, fully corrected paint thanks to Adams Polishes and my hard work. Built with reliability in mind with some power for those times when you need to pass or go over a big hill. Just a poser, not a racer!
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  4. 08-26-2015, 11:59 AM #4
    J Wikoff
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    Yep, I looked up the code. Just don't know what would set it when I have extenders on the rear sensors.
    09 G8 GT SRM Premium Sport Sunroof



    HSV GTS Triple Gauge Pod, GXP Rear Sway Bar and Diffuser, HSV SuperSport Steering wheel, SOLO axle-backs, Magnaflow cats, Red Hot Shift Knob, Auto-dim Mirror, Hood Vent Mod, Removed Intake Cover, Rotofab CAI, Cortex, Infinity door speakers, MTX Re-Q5, Pioneer Amp & RF Sub, LED lows & fogs, Spyder tails, Power Slot rotors, Wagner Thermoquiet pads, Chrome lug covers, Glovebox light,

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  5. 01-22-2016, 08:43 AM #5
    J Wikoff
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    I still get occasional P0420 and P0430 codes. Any thoughts?
    09 G8 GT SRM Premium Sport Sunroof



    HSV GTS Triple Gauge Pod, GXP Rear Sway Bar and Diffuser, HSV SuperSport Steering wheel, SOLO axle-backs, Magnaflow cats, Red Hot Shift Knob, Auto-dim Mirror, Hood Vent Mod, Removed Intake Cover, Rotofab CAI, Cortex, Infinity door speakers, MTX Re-Q5, Pioneer Amp & RF Sub, LED lows & fogs, Spyder tails, Power Slot rotors, Wagner Thermoquiet pads, Chrome lug covers, Glovebox light,

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  6. 01-22-2016, 11:39 AM #6
    Chewy
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    I wouldn't rule out your extensions. I know one of our club members has had issues with his throwing codes intermittently. Does that tuner allow you to turn them off?

    2009.5 MSM GXP 500ish N/A RWHP. Mods include but aren't limited to: Texas Speed 418 (6.8L) fully forged held together with ARP from top to bottom, PRC 255cc heads, Rick Crawford intake plenum, TB port, polish and tune, Roto-Fab 102mm CAI w/LS7 MAF, Kooks 1-7/8" headers wrapped with DEI, Corsa catless system, Circle D 3200 Stall, 3.45 final drive, BMR's complete street bushing kit and sway bars, Eibach Pro Kit, G-Force Axles, running on staggered VMR 710's with Bridgestone RE11 rubber. HSV triple gauge pack with Calais smokers kit mod, V6 tails, debadge/rebadge, V6 door handles, AU black door trim, Maverick Man under hood strut covers, & washer and bolt kit, fully corrected paint thanks to Adams Polishes and my hard work. Built with reliability in mind with some power for those times when you need to pass or go over a big hill. Just a poser, not a racer!
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  7. 01-22-2016, 12:04 PM #7
    J Wikoff
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    It doesn't. It only allows adjustments to a few parameters, and even then, it's "stock or Cortex" as the two choices.

    I put the extenders in on speculation to prevent these codes with the Maggie cats. Do you think they just aren't enough, or they somehow cause the codes?
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    HSV GTS Triple Gauge Pod, GXP Rear Sway Bar and Diffuser, HSV SuperSport Steering wheel, SOLO axle-backs, Magnaflow cats, Red Hot Shift Knob, Auto-dim Mirror, Hood Vent Mod, Removed Intake Cover, Rotofab CAI, Cortex, Infinity door speakers, MTX Re-Q5, Pioneer Amp & RF Sub, LED lows & fogs, Spyder tails, Power Slot rotors, Wagner Thermoquiet pads, Chrome lug covers, Glovebox light,

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  8. 01-22-2016, 12:16 PM #8
    Chewy
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    Quote Originally Posted by J Wikoff View Post
    It doesn't. It only allows adjustments to a few parameters, and even then, it's "stock or Cortex" as the two choices.

    I put the extenders in on speculation to prevent these codes with the Maggie cats. Do you think they just aren't enough, or they somehow cause the codes?
    I wonder if they could be getting wet or something. You double your connections with them which is never good. Worth a check! Maybe spray some WD-40 on them and plug them back in to each other??? Just spit balling here!

    2009.5 MSM GXP 500ish N/A RWHP. Mods include but aren't limited to: Texas Speed 418 (6.8L) fully forged held together with ARP from top to bottom, PRC 255cc heads, Rick Crawford intake plenum, TB port, polish and tune, Roto-Fab 102mm CAI w/LS7 MAF, Kooks 1-7/8" headers wrapped with DEI, Corsa catless system, Circle D 3200 Stall, 3.45 final drive, BMR's complete street bushing kit and sway bars, Eibach Pro Kit, G-Force Axles, running on staggered VMR 710's with Bridgestone RE11 rubber. HSV triple gauge pack with Calais smokers kit mod, V6 tails, debadge/rebadge, V6 door handles, AU black door trim, Maverick Man under hood strut covers, & washer and bolt kit, fully corrected paint thanks to Adams Polishes and my hard work. Built with reliability in mind with some power for those times when you need to pass or go over a big hill. Just a poser, not a racer!
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  9. 01-22-2016, 03:03 PM #9
    J Wikoff
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    By extenders, I mean they extend the bungs in the stock mid-pipe and get the O2 element out of the exhaust stream.
    09 G8 GT SRM Premium Sport Sunroof



    HSV GTS Triple Gauge Pod, GXP Rear Sway Bar and Diffuser, HSV SuperSport Steering wheel, SOLO axle-backs, Magnaflow cats, Red Hot Shift Knob, Auto-dim Mirror, Hood Vent Mod, Removed Intake Cover, Rotofab CAI, Cortex, Infinity door speakers, MTX Re-Q5, Pioneer Amp & RF Sub, LED lows & fogs, Spyder tails, Power Slot rotors, Wagner Thermoquiet pads, Chrome lug covers, Glovebox light,

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  10. 01-25-2016, 05:22 AM #10
    Chewy
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    Quote Originally Posted by J Wikoff View Post
    By extenders, I mean they extend the bungs in the stock mid-pipe and get the O2 element out of the exhaust stream.
    Sorry! I thought you meant the wire extenders.

    2009.5 MSM GXP 500ish N/A RWHP. Mods include but aren't limited to: Texas Speed 418 (6.8L) fully forged held together with ARP from top to bottom, PRC 255cc heads, Rick Crawford intake plenum, TB port, polish and tune, Roto-Fab 102mm CAI w/LS7 MAF, Kooks 1-7/8" headers wrapped with DEI, Corsa catless system, Circle D 3200 Stall, 3.45 final drive, BMR's complete street bushing kit and sway bars, Eibach Pro Kit, G-Force Axles, running on staggered VMR 710's with Bridgestone RE11 rubber. HSV triple gauge pack with Calais smokers kit mod, V6 tails, debadge/rebadge, V6 door handles, AU black door trim, Maverick Man under hood strut covers, & washer and bolt kit, fully corrected paint thanks to Adams Polishes and my hard work. Built with reliability in mind with some power for those times when you need to pass or go over a big hill. Just a poser, not a racer!
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