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  1. #11

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    Quote Originally Posted by daddytech View Post
    I own a 99 tahoe and there is only one cat on it there are however 4 O2 sensors on it. There are 2 in the upper part of the exhaust and 1 on each side of the muffler pipe just before it joins and makes the turn to go to the cat. there are no sensors after the cat what would be the point in that ???
    that just does not sound right, has there been any exhaust work done on the tahoe there should be o2 sensors after the cat

    2003 Z71 Silverado LS
    Access roll up cover
    Bed Rails
    Billet Grill insert
    Bed Rug
    CB with PA system
    Waiting to be installed
    Two 8in RF HX2 punch( would have 12s but they got stolen)

  2. #12

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    Quote Originally Posted by Z71_guy View Post
    that just does not sound right, has there been any exhaust work done on the tahoe there should be o2 sensors after the cat
    In theory the computer sends a quick shot of raw fuel into the combustion chamber as a test. The unburned hydrocarbons make the upstream sensors switch at a very fast rate indicating a rich mixture and also telling the computer the upstream sensors are doing their job.

    The downstream sensors after the cat should not switch rapidly if the cat is working. If the cat is bad the downstream sensors switch rapidly indicating a rich condition and a catalytic converter code is set in memory.

    This is the reason for the sensors after the cat. Correct me if I'm wrong cause I'm getting old. LOL
    Jim

    2004 SILVERADO 2500HD LS
    Pro Comp Leveling Kit
    285-75-16 Cooper ST All Terrains
    Pro Comp Programmer
    Bilstein Shocks
    Linux Bed Liner
    Tinted Windows



    Other rides:

    1967 Landcruiser <350 Chevy>
    1970 Camaro
    1990 Geo Metro Convertible
    2007 FJ Cruiser

  3. #13
    Jr. Engineer
    Join Date
    Jan 2009
    Location
    Rochester, MN
    Posts
    231

    Default

    Quote Originally Posted by daddytech View Post
    I own a 99 tahoe and there is only one cat on it there are however 4 O2 sensors on it. There are 2 in the upper part of the exhaust and 1 on each side of the muffler pipe just before it joins and makes the turn to go to the cat. there are no sensors after the cat what would be the point in that ???
    I think you have your muffler confused as your cat
    99 Silverado Z71 4.8
    2" Suspension lift (Add-a-leafs and leveling keys)
    Long tube headers with 3" offroad Y-Pipe
    Volant Cold Air Intake with Ram Air Intake Tube
    Jet Mass Air Flow Sensor
    Diablosport Predator Tuner

    Previous Truck:
    97 Suburban K1500
    3" Body lift
    2" Suspension Lift (Add-a-leafs and cranked up torsion bars)
    35" Yokohama M/T's
    K&N Intake
    Airraid Throttle Body Spacer
    Hypertech Programmer
    Dual Flowmasters

  4. #14

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    Quote Originally Posted by daddytech View Post
    Run some Sea Foam through it. couple cans of that stuff run through the vaccuum line on your power brake booster then mildly rev the truck once the white smoke starts coming out the tail pipe and keep doing it until the white smoke stops. My wife's suburban was throwing O2 sensor codes and the Cat code too. one can of Sea foam and about 15 minutes later, she was running smooth with no codes at all.

    I agree. 14 bucks worth of seafoam is cheaper than the 65 dollar o2 sensor and the much more expensive cat.

  5. #15
    Master Mechanic daddytech's Avatar
    Join Date
    Mar 2008
    Location
    Portland TN
    Posts
    672

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    Quote Originally Posted by Z71_guy View Post
    that just does not sound right, has there been any exhaust work done on the tahoe there should be o2 sensors after the cat
    no there has been no work done on the exhaust at all and unless i missed something there is no O2 sensors after the cat and no I am not confused cbout what's the Cat and what's the muffler.

    the muffler is clear at the back of the truck, great big old round canister looking job "for now" thinking about putting a flowmaster or two on it later on the cat is up near the headers.
    If i didn't know that for sure and know for sure what an O2 sensor looks like and where it's at I sure wouldn't have the gall to be on here making repair suggestions for people on here like i have.

    most of my posts are usually about things I have either done already myself or helped friends do on thier vehicles. if it's something I don't know anything about at all I won't make any comment about it at all.
    Last edited by daddytech; 03-16-2009 at 03:35 PM.

  6. #16

    Cool Can a o2 sensor failure cause a cat code

    After 1996 all trucks have before and after o2s for OBll compliance. I think you just missed yours. Just run your hand over exhaust from cat back. On my 05 Silverado the passenger side rear o2 is hard to see.

  7. #17

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    Quote Originally Posted by silveradotrailblazer View Post
    After 1996 all trucks have before and after o2s for OBll compliance. I think you just missed yours. Just run your hand over exhaust from cat back. On my 05 Silverado the passenger side rear o2 is hard to see.
    Just make sure that your truck hasnt been running before you do this :D

    Some people forget that part...

    Had a friend who hadnt been able to start his car for a few weeks, I got it running for him... after it was idling for 15 mins he decided to put his hand on the exhaust manifold "I didnt think it would be THAT hot"... lol
    -----------
    Thanks
    Stefan - Beacon, NY

    99 Chevrolet Suburban K1500 LS (My truck)
    5.7L V8
    CarPC, 1.6Ghz Intel Atom, 2GB DDR2 Ram, 250GB Harddrive, GPS, BT, WIFI, OBD2 Reader, 7" Lilliput Touch, 9" Headrest monitors, running Centrafuse.
    348.000 miles

    -Computer Consultant-
    Have any computer problems or questions? Just send me a message and I'll see what I can do :)

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