ID the 4 wires in O2 sensor

Discussion in 'General Motoring' started by # Fred #, Dec 28, 2006.

  1. # Fred #

    # Fred # Guest

    Sorry not Volvo but I know you guys here have great answers. My boy yank the
    wires off the O2 sensor connector by accident when he change out the
    catalytic converter and looks like the color code doesn't follow through
    from O2 unit to the connector to the wire harness.

    So from the O2 sensor pigtail I have 4 wires: two blacks, one green and one
    white. The two blacks has a reading about 10 ohms across it and the green
    and white is open. I assume blacks is the heater with one 12V and the other
    at ground - polarity makes on difference, right? So this left the green and
    white as sensor, right? Green and white polarity makes no difference, right
    also? How many ohms should be measured once I apply some heat to the sensor?
    If polarity counts, how could I find out which is what?

    Sorry for so many questions and thanks in advance.
    # Fred #, Dec 28, 2006
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  2. I'm sure you're right about the black wires, but the polarity is important
    on the other two. The output is a DC voltage that varies between about 0.1
    and 0.9 volts. My guess is that green is ground (negative) and white is the
    signal lead (positive). Maybe the green wire reads low resistance to the
    exhaust, or maybe the white one does?

    Michael Pardee, Dec 29, 2006
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  3. # Fred #

    Tim.. Guest

    Blacks - ground.
    Green - Heater +12v.
    White - Signal +0.1-+0.9v approx.

    Tim.., Dec 29, 2006
  4. # Fred #

    # Fred # Guest

    For the connector to the car I found the 12V and one ground but how to
    verify which terminal is the +signal?

    Also resistance lowers across the green and white terminals as heat is
    applied to the sensor, so shouldn't green be signal ground? Forgot to
    measure output voltage to verify polarity on the sensor.
    # Fred #, Dec 29, 2006
  5. # Fred #

    Mike F Guest

    According to the instructions for a Bosch universal replacement sensor I
    have handy, there are 4 possible OEM wiring colour combos (that this
    universal sensor was designed to replace), your combo is "Type C"

    signal wire = green
    heater wires = black
    signal ground = white

    Mike F.
    Thornhill (near Toronto), Ont.

    Replace tt with t (twice!) and remove parentheses to email me directly.
    (But I check the newsgroup more often than this email address.)
    Mike F, Jan 5, 2007
  6. # Fred #

    # Fred # Guest

    Thanks Mike.

    Is there a way to verify on the car connector which is signal +? If no
    method is available, I'll reverse the terminals when poor mileage is
    # Fred #, Jan 5, 2007
  7. With the ignition on, the signal wire should have about +0.45 volts DC on it
    from the ECU.

    Michael Pardee, Jan 6, 2007
  8. # Fred #

    # Fred # Guest

    Thanks. Car is running fine for a week, lucky guess.
    # Fred #, Jan 6, 2007
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