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Thread: Knock sensor counts when sensor not connected?

  1. #1
    Fuel Injected!
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    Knock sensor counts when sensor not connected?

    Folks-

    I'm seeing in my log there are a few knock sensor counts when the sensor isn't even physically connected.

    Any ideas what would cause this?
    -Phil, in Charleston, SC

    '89 S10 Blazer: SOA SAS: Dana 44s, 5.7L V8, 700R4; 35s, 4.10:1; TBI with 1227747 ECM
    '94 Grand Cherokee: 4.0, 4" lift, 31s
    '90 Jeep Cherokee: In progress: 5.7L V8,700R4,NP231C, D44s. TBI with 1227747 ECM
    '87 Fiero GT: 3.8SC (initial research stage)

  2. #2
    Fuel Injected! Dr_Grip's Avatar
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    You have to provide +5V reference voltage to the knock sensor input. An open wire will be interpreted as constant knocks. Please refer to a wiring diagram for your ECU to find out which pins to connect.

  3. #3
    Fuel Injected!
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    Location
    Charleston, SC
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    Issue has since been resolved via harness repair. Also, there was only one wire going to it..
    -Phil, in Charleston, SC

    '89 S10 Blazer: SOA SAS: Dana 44s, 5.7L V8, 700R4; 35s, 4.10:1; TBI with 1227747 ECM
    '94 Grand Cherokee: 4.0, 4" lift, 31s
    '90 Jeep Cherokee: In progress: 5.7L V8,700R4,NP231C, D44s. TBI with 1227747 ECM
    '87 Fiero GT: 3.8SC (initial research stage)

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