Knock Sensor Issues

Discussion in 'General Chevy & GM Tech Questions' started by A&Ppilot, May 12, 2010.

  1. A&Ppilot

    A&Ppilot New Member

    I have a 2004 Silverado 1500 extended cab 2x4 with the 4.8L V8 engine

    After driving through some serious flooding I starting getting an intermittent check engine light that turned into a stay on engine light. I went to advanced auto and had them pull the code... it was the #2 knock sensor.

    I pulled the truck apart finding water in everything from the airbox to the intake and finally the #2 knock sensor that was completely submerged and rusty. I changed both knock sensors, changed the oil and transmission fluid.

    The light went away for a week or two then came back the codes still saying #2 Knock senor... I have heard a mass airflow sensor could be the culpret. before I spend anymore time and money chasing electrical issues I was hoping to find some answers... The local dealer has been consistent in making all repairs there thus far cost a minimum of 1000.00 usually requiring 2 or 3 trips to get it right so I like to avoid them if I can

    any ideas?
    Last edited: May 12, 2010
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Have you pulled the codes to make sure it is the same issue???
  3. A&Ppilot

    A&Ppilot New Member

    yes its still the #2 knock sensor tripping the light
  4. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Ok just checking.. I would take a look at the intake etc again.. Following the same procedure. I would buy a can of MAF cleaner... That will clean it off quite nicely.. But if you have that much moisture in the intake again you need to take a look at where that water is coming from.. Also a lot of aftermarket parts can be a short lived part. Not all of them just trying to let you know that it isnt uncommon for a part to die prematurely..
  5. bjwelch76

    bjwelch76 New Member

    You may also want to check the wire harness that plugs the knock sensors into the loom. When the knock sensors get replaced, due to the sealing problem that GM has with this area, it is a good idea to replace the plug as well. When my knock sensor 2 died (in a flood as well) the plug ITSELF had water inside it as well!

    Also the rubber plug that sits atop the knock sensor holes needs RTV to help seal the water out.
  6. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Good point.. also some alcohol type contact cleaner will help to pull out any moisture.
  7. A&Ppilot

    A&Ppilot New Member

    I tried to clean out the plug with air I'll check that again the rtv I thought of too

    it's showing low input voltage to knock sensor 2 i'll probably take it into a shop for a dyignostic check at least then I'll know what is causing it to trip for sure rather than blindly throwing parts and labor at it
  8. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Good idea..Since that can get very expensive...

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