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Thread: Middle (?) O2 sensor on CA emissions R/T

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    Default Middle (?) O2 sensor on CA emissions R/T

    I decided to finally install my Mopar Mids on my '99 R/T, and rip the whole exhaust system off. It was stock except for a flowmaster muffler. I have 4 oxygen sensors in the stock system, 2 in the lead pipes and 1 after the cat as I expected. Then I found this extra O2 right in the beginning of the cat where the 2 lead pipes go in. What is the purpose of this O2? I know it's a CA emissions thing, as my first '99 R/T only had 3 sensors.

    When I get my exhaust done next week, I wasn't planning on having this middle sensor put into the system, and eventually want both the "rear" sensors tuned out. What will happen if this middle sensor is not in the system right now? Can I just plug it in and zip tie it to the frame?
    '99 R/T- Red Reg/cab (Procharged garage Queen!)
    '99 R/T- Deep Amethyst Reg/Cab(the daily driver)
    '00 R/T- Blue Ext/cab(The newest arrival)
    '04 SRT4- stage 2, bigger turbo, intercooler, and exhaust
    '91 Dakota- reg/cab short bed(5.2 magnum swap in progress)
    '87 Shelby Charger(will get to it eventually)
    '76 W100- 400/auto(it was given to me)
    '71 D100- short bed(will be getting magnum/OD auto swap)
    '68 A100 pickup- 360/auto


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    G-Man's Avatar
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    I think you will need that 3rd sensor in the pipe (mine is still there) if you read the codes it shows up as sensor 1-2 and 2-2. Kinda wierd I know. The one zip tied to the frame on mine shows up as Sensor 1-3. So basically my scanner shows readings from 5 O2 Sensors.
    I had a problem with that Sensor once and the engine/PCM was NOT happy.
    G-Man
    Disclaimer: this applies to my Federal 1999 R/T

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    Quote Originally Posted by G-Man View Post
    I think you will need that 3rd sensor in the pipe (mine is still there) if you read the codes it shows up as sensor 1-2 and 2-2. Kinda wierd I know. The one zip tied to the frame on mine shows up as Sensor 1-3. So basically my scanner shows readings from 5 O2 Sensors.
    I had a problem with that Sensor once and the engine/PCM was NOT happy.
    G-Man
    Disclaimer: this applies to my Federal 1999 R/T
    How many sensors does your truck actually have? My old '99 R/T only had 3, one in each lead pipe, and one after the cat.
    '99 R/T- Red Reg/cab (Procharged garage Queen!)
    '99 R/T- Deep Amethyst Reg/Cab(the daily driver)
    '00 R/T- Blue Ext/cab(The newest arrival)
    '04 SRT4- stage 2, bigger turbo, intercooler, and exhaust
    '91 Dakota- reg/cab short bed(5.2 magnum swap in progress)
    '87 Shelby Charger(will get to it eventually)
    '76 W100- 400/auto(it was given to me)
    '71 D100- short bed(will be getting magnum/OD auto swap)
    '68 A100 pickup- 360/auto


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    G-Man's Avatar
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    niebs's Avatar
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    how many cats do you have? I have a cat on each bank with a o2 pre and post on each. then the pipe go together to a resonator then to a muffler... well it did haha not no mo.

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    Quote Originally Posted by niebs View Post
    how many cats do you have? I have a cat on each bank with a o2 pre and post on each. then the pipe go together to a resonator then to a muffler... well it did haha not no mo.
    My truck only had one cat on it, no pre-cats. Here's my stock layout:

    Two lead pipes with an O2 in each one, the two pipes go into a single cat that has an O2 right at the front of it(right between the two lead pipes), then a single exit from the cat with the last O2 about a foot away.
    '99 R/T- Red Reg/cab (Procharged garage Queen!)
    '99 R/T- Deep Amethyst Reg/Cab(the daily driver)
    '00 R/T- Blue Ext/cab(The newest arrival)
    '04 SRT4- stage 2, bigger turbo, intercooler, and exhaust
    '91 Dakota- reg/cab short bed(5.2 magnum swap in progress)
    '87 Shelby Charger(will get to it eventually)
    '76 W100- 400/auto(it was given to me)
    '71 D100- short bed(will be getting magnum/OD auto swap)
    '68 A100 pickup- 360/auto


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    G-Man's Avatar
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    Quote Originally Posted by dragbaron View Post
    My truck only had one cat on it, no pre-cats. Here's my stock layout:

    Two lead pipes with an O2 in each one, the two pipes go into a single cat that has an O2 right at the front of it(right between the two lead pipes), then a single exit from the cat with the last O2 about a foot away.
    That's exactly what mine had.
    same as mine.
    Only the last one is hanging.
    G-Man

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    Quote Originally Posted by G-Man View Post
    That's exactly what mine had.
    same as mine.
    Only the last one is hanging.
    G-Man
    Well, I will have all four put back into the system, and when I get a wideband, I'll pull the last one out and leave it plugged into the harness.

    You know, I thought for sure my first '99 R/T only had three O2 sensors, but it has been like 12 years since I had it! Haha
    '99 R/T- Red Reg/cab (Procharged garage Queen!)
    '99 R/T- Deep Amethyst Reg/Cab(the daily driver)
    '00 R/T- Blue Ext/cab(The newest arrival)
    '04 SRT4- stage 2, bigger turbo, intercooler, and exhaust
    '91 Dakota- reg/cab short bed(5.2 magnum swap in progress)
    '87 Shelby Charger(will get to it eventually)
    '76 W100- 400/auto(it was given to me)
    '71 D100- short bed(will be getting magnum/OD auto swap)
    '68 A100 pickup- 360/auto


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    kota360's Avatar
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    I beleive that if you want to put a wide band a/f gage in, you want it to be pre-cat, not post.
    Edelbrock Magnum heads, Harland-Sharp 1:6 RR, Jomar Performance Ultra-Lite Stud Girdle, SoutheastPerformance Sheet Metal Valve Covers, Custom Hyd Roller from Reed Cams, Mopar M-1 2 Brl Intake, Hughes Stage 1 TB, JBA SS Headers, Jacobs Electronics Pro Street Ignition System and Wires, MBRP 'Cuda Style Exhaust, Western Chassis 2" drop front and rear, Edelbrock IAS Shocks, Terry DeLong Pro-Glass Shaker Hood

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    I was gonna start a new tread about this same conversation so if u guys don't mind I have. Few questions.

    Trying to make my truck run a little better. 99 RT single cab. I have mopar mid/long (not sure) headers into. X pip No Cat into two flow masters then out the to the back bumper. Simple

    none of my o2 sensors are leaning against the frame. And yes I have 2 OBD codes on my truck right now. Bank 1 sensor 2 high voltage///// and bank 1 sensor 2 pending.

    Let me know what u guys think

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