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Thread: 7747 convert to 4 wire O2 sensor

  1. #1
    Fuel Injected!
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    7747 convert to 4 wire O2 sensor

    Question about the ground wire specifically. D7 is the signal to the sensor, then D6 goes to engine ground. When converting to a 4 wire, do I just run the sensor signal ground back to D6 and eliminate the engine ground? Logic is telling me yes, but I know GM engineers weren't always logical.

  2. #2
    Super Moderator dave w's Avatar
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    2002 Vortec 5.0 liter _ 5.7 liter 4 wire O2 sensor wiring diagram attached.

    dave w
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  3. #3
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    Quote Originally Posted by dave w View Post
    2002 Vortec 5.0 liter _ 5.7 liter 4 wire O2 sensor wiring diagram attached.

    dave w
    Thanks Dave. That confirms what I was thinking.

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    Super Moderator dave w's Avatar
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    I'm not sure what to say about the "Resistor" shown in the "Low Reference" side of the 4 wire O2 sensor that is also tied to the case ground. Likely the 1227747 does not have such circuitry.

    I like the 3 wire O2 sensor, signal to ecm, ground for heating element, and ignition 12 volts for the heating element. Most 1995 GM Pickups with 4.3 liter V6 have the 3 wire O2 sensor.

    dave w

  5. #5
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    Yes, if the element in the sensor is grounded. Basically, check the sensor itself from the plug wire (A pin?) to case is a short.

    It's been a while, but I recall looking at the O2 circuit and finding it was a fully differential op-amp configuration when I did look at a schematic. I don't even know where to find the old ECM schematics anymore. Isn't the Ludis site gone?
    Last edited by lionelhutz; 05-10-2021 at 07:34 PM.

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