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Oxygen Sensor testing issue

Discussion in 'Boxers/TR/M' started by 4heid, Oct 26, 2019.

  1. 4heid

    4heid Rookie

    Jul 31, 2019
    46
    Maryland
    Full Name:
    Chris
    I am using Diagnostic Sheet 6 to test some final values and when I use test #5 which tests pins 7 and 8 to record the resistance of the oxygen sensor, I only get an O.L. value, for both sensors.
    If I check the connector on the sensor itself, testing the 2 white heater leads, the resistance between them is about 4 Ohms.
    Has anyone had this issue at the ECU?
     
  2. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,764
    Texas
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    Steve Magnusson
    #2 Steve Magnusson, Oct 26, 2019
    Last edited: Oct 26, 2019
    You are misreading your result (and doing the wrong test). Measuring between pins 7 and 8, you should get a result > 1 Meg Ohm when cold. A result of "O.L." on your meter is > 1 Meg Ohm so all is OK. Measuring between pins 7 and 8 at the injection ECUs is the same as measuring between the single signal wire of the O2 sensor and the metal body of the O2 sensor. The two white internal heater leads of the O2 sensor are not part of this test.

    PS Even if you had a bad O2 sensor, it would have nothing to do with cold start-up and cold-running (coolant temp less than about 160 deg F on the dash gauge). If your symptom was good running when cold, but bad running when the coolant temp got to ~160 deg F = then the O2 sensors might be bad.
     
  3. 4heid

    4heid Rookie

    Jul 31, 2019
    46
    Maryland
    Full Name:
    Chris
    Steve, you are right. I also missed some info.
    I tried heating the oxygen sensor element with a small torch and the resistance didnt change. Clearly they are originals and one had a bad signal connector, the single wire, so i will fix it in any case.
     

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