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  1. #1

    Default those nasty knock sensors

    hello, anyone ever changed coded knock sensors just to have them code a few days later? mine are new and now have both coded again. my truck is a 2003 gm 3/4 ton 4by, 279000kms. of coarse i've checked the harness for issues, don't see any visible ones. i not sure where to go next. i'd be gratful for any advise. thanks

  2. #2
    Master Mechanic tattooed4life's Avatar
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    Default

    I have heard of sensors going bad and "spiking" the computer. You then replace the sensor only to have this happen again but now instead of a bad sensor there is a "spike" in the computer which ruins a new sensor. I am not sure if this can happen with a knock sensor and "spike" is not the technical term for what I was told happened to my G/F's car but the situation is the same. I had to replace the computer to fix the problem.
    1997 Chevy K3500
    4x4 X-Cab Dually
    454 Dual Exhaust

  3. #3

    Default

    dealing with the same issue except my code just went away and i didn't replace anything. The GM tech at the service garage told me that my intake gasket was worn allowing water get in and mess with sensors and harness. Is there anything loose that could be rattling on your motor? Maybe something is causing vibration that shouldn't and keeps setting off the sensors.
    Just a yank in the heart of DIXIE

  4. #4

    Default

    Usually when a knock sensor code sets it's not a bad knock sensor. I see people change knock sensors for no good reason quite frequently. The code sets when the sensor hears a knock and the PCM trys to quiet it by retarding the timing. If the knock is still there after the timing has been retarded the code sets. Any noise belts, tensioners, lifters, exhaust, boom boxes will set knock sensor codes.
    Jim

    2004 SILVERADO 2500HD LS
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    Other rides:

    1967 Landcruiser <350 Chevy>
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  5. #5

    Default

    Quote Originally Posted by tattooed4life View Post
    I have heard of sensors going bad and "spiking" the computer. You then replace the sensor only to have this happen again but now instead of a bad sensor there is a "spike" in the computer which ruins a new sensor. I am not sure if this can happen with a knock sensor and "spike" is not the technical term for what I was told happened to my G/F's car but the situation is the same. I had to replace the computer to fix the problem.
    GM PCMs have self protected drivers that act as circuit breakers to prevent a shorted sensor from damaging the PCM.

  6. #6

    Default

    thanks for the info. i do have a ticking idler and squeeking belt. i'll change these things and see what happens.

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