02 sensor heater resistance learn reset

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  • autojoe
    Member
    • Oct 2012
    • 68

    02 sensor heater resistance learn reset

    P0036 P0054 new 02 sensor bank 1 sensor 2.....codes come back. Looked in service information and found this.... Notice: When replacing the HO2S perform the following:

    A code clear with a scan tool, regardless of whether or not a DTC is set
    HO2S heater resistance learn reset with a scan tool, where available
    Perform the above in order to reset the HO2S resistance learned value and avoid possible HO2S failure. I have never seen this before in my snap on solus pro. Do you need a tech 2?
  • Joe Rappa
    Snap-on DSD
    • Aug 2007
    • 2050

    #2
    No need for the Tech 2.
    This coverage was added in 2011. If your Solus Pro is updated past that, it will have the coverage. As GM instructs, you are supposed to command the Heater Relearn before you move or replace any heated O2 sensor. As an alternative to the reset, you can just clear the codes(even if there aren't any to clear) and it does the same thing.
    If you can read O2 heater amps with your scanner on a GM vehicle, then it has the RCOHT (Resistance Calculated O2 Heater Temp) setup. The PCM controls the O2 heaters on these vehicles.
    Here's the reason for the reset: On early GM vehicles, if the key was on, so were the O2 heaters. They'd get hot in 30-60 seconds. These new ones get hot in as little as 6 seconds. In order to do that, the PCM controls the circuit, so they can get hot fast, and then not burn up.
    On a cold start, the PCM calculates the resistance thru the O2 heaters, and makes a decision on how to run them for that drive cycle. Because it only does this test on a cold start, if you moved an O2 to a different spot, it would now have an incorrect heater strategy. I can't imagine it's that big of a deal...but that's what it is.
    On a more important note, some PCMs are programmed so that if an O2 heater fails open (which is common) the PCM will turn that O2 on continuously in order to get whatever heat out of it that it can.
    If you replace that O2 without doing the reset, it will burn the heater open in a few minutes. So, before you plug any new O2 into one of these vehicles, it is safest to do the reset before you connect it. clearing the codes does the same thing.
    Joe
    Attached Files
    "You don't build a reputation on what you're going to do"
    Henry Ford

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    • Witsend
      Banned
      • Nov 2012
      • 2942

      #3
      You would think if doing this procedure was such a critical thing to do to prevent the internal heating element from flashing out within a few minutes that the replacement O2 sensors would come with a sheet of paper with explicit warnings about consequences of not performing this procedure.

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      • autojoe
        Member
        • Oct 2012
        • 68

        #4
        Thanks Joe for all your helpful information. I appreciate it very much. Joe

        Comment

        • Joe Rappa
          Snap-on DSD
          • Aug 2007
          • 2050

          #5
          Originally posted by autojoe
          Thanks Joe for all your helpful information. I appreciate it very much. Joe
          No problem.
          "You don't build a reputation on what you're going to do"
          Henry Ford

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