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  1. #1

    Default Can a O2 sensor failure cause a Cat code?

    Hey,

    I took my 99 burban to get it inspected today.

    FAILED lol... check engine light was out, and they plugged the OBDII reader into it.

    Came back with
    P0161 (O2 Sensor Heater Circuit Bank 2 Sensor 2)
    P0420 Catalyst System Efficiency Below Threshold Bank 1
    P0430 Catalyst System Efficiency Below Threshold Bank 2

    Could the problem with the O2 Sensor cause the code for the Cat to show or do I have to replace the cats ?
    -----------
    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 :)

  2. #2

    Default

    Yes it sure can. The O2 sensor before the cat measures the Hydrocarbons before the cat and the Downstream O2 "sees" if the cat is working. A bad upstream sensor can cause the cat code.
    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. #3

    Default

    Quote Originally Posted by Jimmiee View Post
    Yes it sure can. The O2 sensor before the cat measures the Hydrocarbons before the cat and the Downstream O2 "sees" if the cat is working. A bad upstream sensor can cause the cat code.
    Correct me if I am wrong, but isnt Sensor 2 Bank 2 the O2 sensor on the passenger side, after the cat, no before the cat?

    Also, the 99 Suburban (K1500 with R motor, 350) doesnt it have two cats?
    -----------
    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 :)

  4. #4

    Default

    Quote Originally Posted by Bredin View Post
    Correct me if I am wrong, but isnt Sensor 2 Bank 2 the O2 sensor on the passenger side, after the cat, no before the cat?

    Also, the 99 Suburban (K1500 with R motor, 350) doesnt it have two cats?

    I believe your right about the location of the O2, if the truck is the old body style 99' with the 5.7 there should be two cats(my 97 did and its the same motor)

    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)

  5. #5

    Default

    Quote Originally Posted by Z71_guy View Post
    I believe your right about the location of the O2, if the truck is the old body style 99' with the 5.7 there should be two cats(my 97 did and its the same motor)
    Yup, old body style, not the rounded one with less interior room and the 5.7L...

    So I guess I should go with new cats uh :(
    -----------
    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 :)

  6. #6

    Default

    Quote Originally Posted by Bredin View Post
    Yup, old body style, not the rounded one with less interior room and the 5.7L...

    So I guess I should go with new cats uh :(
    I didn't realize it had 2 cats. I would still make sure the O2 sensor is working correctly before changing the cats.< jmo>
    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

  7. #7

    Default

    Quote Originally Posted by Jimmiee View Post
    I didn't realize it had 2 cats. I would still make sure the O2 sensor is working correctly before changing the cats.< jmo>
    Yup, gonna do that first too.... new O2 sensor is $65 with lifetime warranty... cat is alot more lol
    but I think I can get it at the junkyard for free :x
    -----------
    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 :)

  8. #8
    Jr. Engineer
    Join Date
    Jan 2009
    Location
    Rochester, MN
    Posts
    231

    Default

    You could try swapping the O2 sensors and see if the code moves over to the other bank. If it does, then you know you need an O2 sensor, if not then you may want to get a new 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

  9. #9
    Master Mechanic daddytech's Avatar
    Join Date
    Mar 2008
    Location
    Portland TN
    Posts
    672

    Default

    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.

  10. #10
    Master Mechanic daddytech's Avatar
    Join Date
    Mar 2008
    Location
    Portland TN
    Posts
    672

    Default

    Quote Originally Posted by Z71_guy View Post
    I believe your right about the location of the O2, if the truck is the old body style 99' with the 5.7 there should be two cats(my 97 did and its the same motor)
    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 ???

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