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  1. #1
    Active Member Two Rings
    Join Date
    Mar 05 2018
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    415013
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    Czech Republic

    Knock sensor part numbers

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    Hi, could someone please tell me the part number of knock sensor 2 and 4 on my B6 S4? Or on which side of the motor are they located? I know that they are under the IM but dont know which one is which.


    Thnaks for your help.

  2. #2
    Senior Member Two Rings PigDiesel54's Avatar
    Join Date
    Jan 18 2013
    AZ Member #
    107784
    Location
    CT

    FRONT RIGHT = 079905377G
    FRONT LEFT & RIGHT REAR = 079905377E
    LEFT REAR = 079905377H

    Per ECStuning
    2006 Brilliant Red B7 S4 Avant 6MT
    2001 Cactus Green B5 S4 Avant 6MT
    2006 Brilliant Red B7 A4 2.0T Quattro Tiptronic

  3. #3
    Active Member Two Rings
    Join Date
    Mar 05 2018
    AZ Member #
    415013
    Location
    Czech Republic

    Yeah, but I need to know which one is, according to VAG, knocks sensor 2 (code 16716) and knock sensor 4 (code 17731)

  4. #4
    Senior Member Two Rings PigDiesel54's Avatar
    Join Date
    Jan 18 2013
    AZ Member #
    107784
    Location
    CT

    [IMG][/IMG]
    2006 Brilliant Red B7 S4 Avant 6MT
    2001 Cactus Green B5 S4 Avant 6MT
    2006 Brilliant Red B7 A4 2.0T Quattro Tiptronic

  5. #5
    Veteran Member Four Rings q_dubz's Avatar
    Join Date
    Dec 16 2008
    AZ Member #
    36417
    My Garage
    Single Turbo V8 S4
    Location
    EAST COAST

    Before you just go replacing the sensor. Check the wiring connections.

  6. #6
    Active Member Two Rings
    Join Date
    Mar 05 2018
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    Wiring was checked. But I will look again. Thank you so much for the picture.

  7. #7
    Veteran Member Four Rings q_dubz's Avatar
    Join Date
    Dec 16 2008
    AZ Member #
    36417
    My Garage
    Single Turbo V8 S4
    Location
    EAST COAST

    BTW, what were the codes being thrown?

  8. #8
    Active Member Two Rings
    Join Date
    Mar 05 2018
    AZ Member #
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    Czech Republic



    Maybe retorque could help but probably not. I will be doing the oil check valves so i wanted to fix this too.

  9. #9
    Veteran Member Four Rings q_dubz's Avatar
    Join Date
    Dec 16 2008
    AZ Member #
    36417
    My Garage
    Single Turbo V8 S4
    Location
    EAST COAST

    have you ever removed them?

    Torque should be at 20Nm / 14.75ft-lbs

  10. #10
    Active Member Two Rings
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    Mar 05 2018
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    Czech Republic

    Yes they were removed during the engine rebuild. During the rebuild the ECU was flashed with OEM firmware because there was wrong firmware(maybe a tune) and the car was sputtering. After the flash the codes were thrown. But the sensors could be bad for a long time because the car was down on power when I bought it.

  11. #11
    Veteran Member Four Rings q_dubz's Avatar
    Join Date
    Dec 16 2008
    AZ Member #
    36417
    My Garage
    Single Turbo V8 S4
    Location
    EAST COAST

    Quote Originally Posted by Padouch View Post
    Yes they were removed during the engine rebuild. During the rebuild the ECU was flashed with OEM firmware because there was wrong firmware(maybe a tune) and the car was sputtering. After the flash the codes were thrown. But the sensors could be bad for a long time because the car was down on power when I bought it.
    nah, they are merely a vibrating crystal (in simple terms) they don't fail from not being powered. That code tells me they weren't torqued properly.

    They're EXTREMELY sensitive to torque. Mine were over torqued (bad torque wrench or i did 20lb/ft instead of Nm) and I was seeing knock correction at idle LOL

  12. #12
    Active Member Two Rings
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    Mar 05 2018
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    I meant that they could be coded out for the sale and bad long before. The car was kind of pile of shit on closer inspection :) but the price was right

  13. #13
    Active Member Two Rings
    Join Date
    Mar 05 2018
    AZ Member #
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    Czech Republic

    So progress has been made. I replaced the oil check valves (fixed my warm rattle and cold rattle is almost gone too) and replaced all 4 knock sensors. But still getting codes from Knock sensor 1, 2 - signal too low. There were codes for knock sensors 2, 4 before. So sensor 4 is gone but 1 instead.

    All 4 were torqued to 24 Nm (Should be 20-25Nm right?).

    Should I try to tighten them a little?

    Or maybe my previous idea was right? https://www.audizine.com/forum/showt...ild-S4-B6-Cats

    Im hopeless. The car drives great when cold.

    Appreciate any help.

    //edit
    What VAG block shows the actual values from knock sensors?

  14. #14
    Veteran Member Four Rings q_dubz's Avatar
    Join Date
    Dec 16 2008
    AZ Member #
    36417
    My Garage
    Single Turbo V8 S4
    Location
    EAST COAST

    20Nm as I said BEFORE.

    Also you have a wiring issue.

    Blocks 26+27 I think is voltage.

  15. #15
    Active Member Two Rings
    Join Date
    Mar 05 2018
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    Oh sorry. ECS instructions said 25Nm. I drove the car today and this time sensors 1,2,4 appeared. I'll try to torque them to 20Nm. Thanks again

  16. #16
    Active Member Two Rings
    Join Date
    Mar 05 2018
    AZ Member #
    415013
    Location
    Czech Republic

    So once again thanks for your help. I torque the sensors to 20Nm and it really helped. The car drives like never before, but still getting code for sensor 4 and wiring is OK. Do you know which block shows the timing pull? Could a plugged cat trigger knock sensors?

    //Edit
    Found the blocks for timing retard 10,20,21
    And what voltages should I see from the Knock sensors in block 26,27?

  17. #17
    Veteran Member Four Rings q_dubz's Avatar
    Join Date
    Dec 16 2008
    AZ Member #
    36417
    My Garage
    Single Turbo V8 S4
    Location
    EAST COAST

    Quote Originally Posted by Padouch View Post
    So once again thanks for your help. I torque the sensors to 20Nm and it really helped. The car drives like never before, but still getting code for sensor 4 and wiring is OK. Do you know which block shows the timing pull? Could a plugged cat trigger knock sensors?

    //Edit
    Found the blocks for timing retard 10,20,21
    And what voltages should I see from the Knock sensors in block 26,27?
    Knock voltage is a black art but it's good to compare how close they are.

  18. #18
    Active Member Two Rings
    Join Date
    Mar 05 2018
    AZ Member #
    415013
    Location
    Czech Republic

    Still no luck with the sensors 1 and 4. The voltages are under load are completely different. cylinders 1,2 and 7,8 are max 1V, but usually below and other cylinders are around 6-8V under load and around 1V when idling.

    Will check the wiring again. Does anyone know which pin on ECU should I check? Or do I have to follow the wire?

    Still not sure about the exhaust because it drives fine when cold. Found some DIY to remove downpipes and it does not look easy without lift :).



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