Question about 1997 Subaru Legacy

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Downstream O2 What color wire on the factory wiring harness is the signal wire (black) on the downstream O2 sensor?

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Mine is yellow. I just went out and looked.

Posted on Feb 05, 2009


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Found out I'm missing drivers side upstream o2 downstream was there some help to find the missing wire be awesome

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Year make and model would be helpful for any information.
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The wires on the o2 sensor i removed is different from the replacement i purchased

ask the parts guys if they have another brand and compare.

I have changed them, and although some wires may be a different color, if the plug fits, it should work.
Check another brand first to see the color and try to avoid Bosch as they seem to brake often shortly after the warranty expires on them.

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O2 sensors wiring diagrams

Locate the wires running off from the O2 sensor. There should be two. The black wire is the ground wire. The other wire, which may vary in color, supplies power to the sensor.

  • 2 Connect the power lead to the corresponding connector on the chassis's wiring harness.
  • 3 Connect the black, or ground, lead to the corresponding connector on the factory wiring harness.
  • 3 wires, "how do i wire it" are simply explained. all universal 3 wire o2 sensors will have 2 wires one color, the other wire a different color. the 2 that are the same color are ground and power for the heater and it doens't matter which one is which. so ground to the motor, power from the gray wire on the fuel pump, or anywhere you want to pull 12 volts while the car is running. i have a dedicated fan relay that doesn't use the ecm and runs off the key, so thats where i went. the different color wire goes to the stock sensor wire, it's the signal.

  • Dec 04, 2011 | 1989 GMC K3500

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    Bosch 02 sensor downstream on a 1996 Jeep grand cherokee 4.0 motor. I have no wire harness to match the colors to. bosch has two white, one grey and one black. Jeep has orange/green,black/brown,black/blue...

    The two white are the heater
    The black the ground
    The gray the O2 Sensor output,
    you back probe to check Voltage
    & Switching Times

    The vehicle wiring harness does not have to match
    the sensor, BUT -- you need to have the same
    connector on the sensor

    If you have a universal cut & splice, you have junk,
    and we given the wrong part

    Get a Bosch or NGK, OEM sensor & just
    plug it in

    Jun 23, 2011 | Jeep Grand Cherokee Cars & Trucks

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    My 1999 honda odyssey have a light on in the check engine, i went to the mechanic & plug it to the small computer, the computer said no response to code P0138B BANK 1 SENSOR 2 HIGHT VOLT, the mechanic...

    There is are upstream and downstream O2 sensors. 1 or 2 (upstream) before the catalytic converter which sends signals for closed loop fuel control and OBD II monitoring, and 1 (downstream) after the catalytic converter, which is used to monitor the catalytic converter operation. The PCM monitors the signal from each O2 sensor.

    Nov 02, 2010 | 2006 Honda Odyssey

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    Universal o2 censor has 2 white 1gray 1black existing wires areblack/tan dkgreen/orng blk/ltbl blk/pink

    First what do you mean by a universal o2 sensor? You must make sure that you have the right o2 sensor, most newer vehicles have four o2 sensors 2 upstream and 2 downstream, upstream and downstream are meant to show where the sensors are in relation to the catalatic converter,some o2 sensors have 1 wire or up to 4 wires most with four wires are heated o2 sensors so you need to be sure you ve gotten the right o2 sensor for you vehicle as well as the right replacement for the proper location! My experience is that most after market o2 sensors have the same colored wires as the vehicle. Also most o2 sensors have electrical plugs? If you need help finding the right o2 sensor for your vehicle then please dont be affraid to ask!

    Feb 12, 2010 | 1996 Jeep Grand Cherokee

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    My oxygen sensor on my 03 Honda Element failed. How do I replace it myself?

    Your Honda has two O2 sensor's, you will need to find out which one is bad, you have an upstream and a downstream, the upstream is the one between the exhaust manifold and the catalytic converter, and the downstream is the one after the catalytic.It's best to have an O2 sensor socket but if you don't have one an 7/8 wrench will work, disconnect O2 sensor harness and unscrew right out, install new sensor and reconnect harness.

    Jan 22, 2010 | 2003 Honda Element

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    O2 Sensor

    Well, Bank 1 is the passenger side of the vehicle. Are you replacing upstream or downstream 02 sensor?

    The upstream is in the exhaust manifold. The downstream is further down in the exhaust pipe. Upstream would be designated by the code HO2S1- B1 and the downstream would be indicated HO2S2-B1.

    In either case, you basically unplug the wiring connector, use a 7/8 wrench (or an O2 sensor socket which has a groove cut in the side to allow the wiring to not be pinched) and loosen the sensor and install the new one (with anti-seize on the threads) and plug the connector in.

    The upstream sensor is pretty easy- the downstream can be a little more difficult, but is not too bad.

    Hope this is helpful!!

    Nissan Scope Technician- 10+ years experience in Nissan dealership.

    Oct 28, 2008 | 2002 Nissan Xterra

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