What do these O2 sensor readings mean?

Discussion in 'General Chevy & GM Tech Questions' started by fulltimer, Sep 26, 2011.

  1. fulltimer

    fulltimer New Member

    I have been trouble shooting an 0420 code on my 2003 Chev Suburban (5.3, 4x4).

    I removed the two o2 sensors on the vehicle passenger side.

    I moved the two sensors from the driver side to the passenger side (P0420 indicates one of these may have problems).

    I put 2 new sensors on the driver side.

    Here are some of the readings I am getting on the front sensors below.

    BANK 1
    Rich to lean sensor switch time Bank 1/S1 = Value .064 sec / Max .14 sec
    Lean to Rich sensor switch time Bank 1/S1 = Value .032 sec / Max .204 sec

    BANK 2
    Rich to lean sensor switch time Bank 2/S1 = Value .024 sec / Max .144 sec
    Lean to Rich sensor switch time Bank 2/S1 = Value .016 sec / Max .204 sec

    The voltage sensor values for each bank are fairly close.

    Not sure what the TID $70 and $71 read, but they are 119/119 on Bank 1 and 132/146 on Bank 2.

    With my inexperience dealing with these numbers, I would say that the new sensors I put in are operating slower than the old sensors. I would think that is a bad thing. Is it enough of a difference to pull the new/slow sensors out and return them for a different brand?

    Anyone that knows what these numbers mean, have any suggestions?

  2. Caddiac

    Caddiac Epic Member 5+ Years 1000 Posts

    Okay there is a few years between our trucks but I would think they are similar enough here that the information from my factory manuals will at least be applicable.

    The P0420 code "Catalyst system low efficiency bank 1" means that the control module is seeing the switch time occur faster than it should and as a result the catalytic converter not performing properly. So slower is better. That may or may not mean that the cats are bad. On my 98 burb which has a different engine, this code is indicating that the cat is bad or there is something causing the cat to appear to be bad.

    Are there any other engine codes or is this the only one? Does your engine use oil? Any symptoms of of an ignition problem like misfires, higher than normal fuel consumption, etc. worn or damaged wiring in the harness (before the sensor connectors) could be another source. A long shot granted but it is possible.

    How many miles are on your engine? Any engine, intake or exhaust mods made recently?
  3. fulltimer

    fulltimer New Member

    My engine has 113,000 miles. I have only had it for a month or so, but it appears to have no modifications. There are no other engine codes coming up. The engine does not seem to be using oil. Last owner never mentioned anything about it either. I have gotten about 17mph on road trips. Wiring right at the sensor connectors all seems in tact and very clean.

    Since I have gotten it, the main thing I had done was replace the dash gages and DIC. My mechanic said that it died on him a couple times while he was driving it during that process. He said that he cleaned the MAF sensor. After the gages had been programmed at the local dealership, it has never died again.

    I never considered the idea that slower switching may be a good thing...

    My understanding has been that the sensors give the control module the readings on oxygen levels before and after the cat. If the reading is the same, or too similar, then it makes the control module think there is a problem. The problem is diagnosed as the cat not working efficiently because the pre and post readings are too similar, when they should be very different. The information that the control module uses is the amount of oxygen present, not the speed that the sensors need to operate at. I thought that the faster the sensors worked, that would mean that the fuel mixture was kept more accurate and give better fuel mileage. If the sensors operate slower, the fuel mixture would not be adjusted as quickly and mpg would suffer. The usual description I read of a sensor that starts to go bad is that it is "sluggish".

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