DIY Oxygen Sensor Replacement?
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  1. #1
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    DIY Oxygen Sensor Replacement?

    Does anybody have any DIY pictures on how to find and replace the oxygen sensors for a '01 Passat? I crawled under the car but could not find anything obvious.

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  3. #2
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    1.8T or V6?

    Which 02 sensors -- (pre-cat or post-cat)?

  4. #3
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    1.8T (Pre-Cat)

  5. #4
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    I just spent 1 hour under the car looking for the sensor. After a while, I even took off
    the plastic cover under the front part of the car. I took lots of pictures, but still can't find this stupid thing. I think it's time to take a visit to the library and see if they have a shop manual.

  6. #5
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    "(Pre-Cat)"

    Unless I am forgetting something there is one right behind the CAT and one further downstream. I cannot rememeber honestly though. I probably need to swap mine too (at 132K miles) Just follow out the side of the engine on the passanger side of the engine bay and look for the electrical wires near the exhaust pipes.

  7. #6
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    The cat is located very close to the exhaust manifold for quick warmup. I believe that you will be able to find the pre-cat O2 sensor by looking under the hood, not under the car. You may even be able to find a post-cat O2 sensor under the hood.

  8. #7
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    You can see the pre-cat 02 by looking down at the turbo area with the hood open. The metal-sheathed wire that plugs into the exhaust just after the turbo is the 02 sensor.

  9. #8
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    Is the pre-cat very difficult to get to? Do I need to remove any covers?

  10. #9
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    You can reach right in and grab it (once it's cooled down).

    Pop your hood and take a look - it's right there behind the turbo.

  11. #10
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    Thanks pete1!!

  12. #11
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    Does the front O2 sensor have 4 or 5 wires? If I stand in front of the car and reach in
    with my left hand, I can touch 1 of the O2 sensors without any trouble. There is another O2 sensor more towards the back and a bit lower. This one is a bit more difficult to get to. The BOSCH O2 sensor that Autozone sold me has only 4 wires, which would match up against the sensor that is toward the back. Did they sell me the wrong part or am I looking at the wrong sensor? The part that I have is BOSCH part# 15733.

  13. #12
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    I'm assuming you have an AWM engine...

    Front O2 sensor has 6 wires: white, yellow-red, green-yellow, red-white, brown, yellow-green. This is the vertical sensor that you can grab easily.

    Post-cat O2 Sensor has 4 wires: green-yellow, white-green, lilac, red. This is the sensor that is sideways, kinda back behind the engine, and harder to get to.

    The part they sold you is the post-cat O2 sensor. Do you have a scan-tool printout of your error codes? Post your DTC "Pnnnn", if you have them.

    AUG engine is remarkably similar... ATW is a little bit different.

  14. #13
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    I have an AUG engine. The code that I pulled is P0135. The wires that I saw
    coming from the front 02 sensor had a red and yellow wire and 3 other colors.

  15. #14
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    I'll check w/ my Bentley manual tonight and post more info.

  16. #15
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    I called Bosch and they told me that I need part number 17090, which is a 5 wire sensor. They said that this is what is used with the AWM. I know mine is an AUG. I am a bit hesitant to order anything if I am unsure.

  17. #16
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    Bentley showed 4-wire for the post-cat and 6-wire for the pre-cat 02 sensors on an AWM.

    Bosch might not consider the ground lead (brown) as a "wire". :???:

    Where are you looking for the wires? ...at the sensor end or at the wiring harness?

    How many "pins" are on the wiring harness of the O2 sensor you have?

  18. #17
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    At each end I see the following wires: white, white, black, grey, red, yellow. I have not taken the wiring harness out yet. Bosch says that the 6th wire is inside the harness and is connected to a resistor and may not be visible. I am still confused by the fact that I have an AUG with a 5 wire sensor.

  19. #18
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    sorry for the delay in posting again...

    The AUG uses a 6-pin harness for the front (pre-cat) O2 sensor, just like the AWM. They both use 4-pin harnesses for the post-cat sensor.

    AEB and ATW use 4-pin harnesses for both.

    Looking at the bentley diagram, it is possible that one of the pins could be jumped to the other inside of the O2 sensor's wiring harness -- leaving 5 wires to actually run from the wiring harness to the sensor body itself.

    The VW OEM wire colors for the O2 sensors vary from engine to engine, even where the electrical function appears to be identical . Also, the bosch sensor could use whatever wire colors bosch wanted, so lining-up by wire color is probably not going to help.

    If bosch says their 5-wire is the right part, I'd go ahead and install it.

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