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Thread: No reading from knock sensor.

  1. #1
    Tuner in Training
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    Unhappy No reading from knock sensor.

    I've tried various tunes and have yet to get a reading from my knock sensor in hp tuners. I've checked the wiring and all is good, the knock sensor is brand new too. I threw my old 4.3 knock sensor on(different part #, but I know it works) and same outcome. Why is this?

    2000 S10 Blazer
    350 Vortec

  2. #2
    Senior Tuner
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    No Knock?
    hard to tell with out log or tune posted

  3. #3
    Advanced Tuner Shrek's Avatar
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    If memory serves the S10 used a Flat Response (LS2 style) knock sensor - at least the 2001+ models did - not sure about your 2000 S10.

    The L31 Vortec engines used a Resonant (LS1 style) knock sensor. These are very different, and require different programming. This is the same issue people run into when trying to use a PCM to control a 24x LS2 engine.

  4. #4
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    Here's the current tune and matching log.

    If memory serves the S10 used a Flat Response (LS2 style) knock sensor - at least the 2001+ models did - not sure about your 2000 S10.

    The L31 Vortec engines used a Resonant (LS1 style) knock sensor. These are very different, and require different programming. This is the same issue people run into when trying to use a PCM to control a 24x LS2 engine.
    All I can tell you is that I have a 1 wire knock sensor. I seen that the 5.7 and 4.3 sensors are different so I got a 5.7, but no change. I'm wondering if maybe I need one from an 02 Express van...
    Attached Files Attached Files
    Last edited by zq8blazer; 04-27-2013 at 08:23 PM.

  5. #5
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    I was just told by a guy that did the same exact swap as me (only he has a 96 model Blazer) that he has his knock sensor wire plugged into C1 Blue 9 and he's getting a reading. He put it into C1 Blue 51 (where I have mine) and he didn't get a reading either.

  6. #6
    Advanced Tuner Shrek's Avatar
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    If the calibration is configured for Resonant (LS1) style knock sensor(s) - then the input from the lone knock sensor on a 2002 Vortec 5.7L engine (or the bank 1 knock sensor on an LSx engine) - is wired to C1 (Blue) pin 51.

    If the calibration is configured for Flat Response (LS2) style knock sensor(s) - then the above would be wired to C1 pin 9.

    Mixing and matching knock sensor types with calibration setting types would yield unusable (or absent) knock sensor data.

  7. #7
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    Thank you so much for clearing that up! Now how can I find out if mine is calibrated for resonant or flat response? Do I just need to try it in C1 Pin 9 or is that too dangerous to attempt?

  8. #8
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    Well I tried putting the wire into #9 and still got the same outcome.

  9. #9
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    I just checked the wire from the pcm to the knock sensor connector (since I had to extend it for the swap) and it's good. Put a ground to the knock sensor and banged around the engine. No reading whatsoever.

  10. #10
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    You need to try a Resonant (LS1) style knock sensor(s) on C1 (Blue) pin 51.
    and if no go
    a Flat Response (LS2) style knock sensor(s) on C1 pin 9.

  11. #11
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    Thought I'd bump this. I'm still having the no knock reading problem. Since the 350 Vortec sensor was under warranty I went and picked up another one. I'm getting a reading from it, but the PCM does not detect it. I hooked up a timing light and the timing doesn't change when I hit the block with a wrench. So here's where I'm at:
    -Verified the wire is in the correct spot.
    -Tried two different knock sensors.
    -Checked for continuity from the knock sensor connector to the pin.
    -Hooked a timing light up and banged on the engine, nothing happened. The notch on the balancer is about 1" before the mark on the timing cover though, idk if that matters.
    -Checked to see if sensor is putting out a voltage.
    -Checked to see if PCM is reading the knock sensor (it is not)


    You need to try a Resonant (LS1) style knock sensor(s) on C1 (Blue) pin 51.
    and if no go
    a Flat Response (LS2) style knock sensor(s) on C1 pin 9.
    I'm 100% positive it requires the one I have in blue pin 51.
    Last edited by zq8blazer; 07-01-2013 at 07:14 PM.

  12. #12
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    also how do I tell if it's tuned for the resonant or flat response knock sensor? As stated it needs to be for the LS1, single wire.

  13. #13
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    I am also having this issue with an LQ4. Any updates?