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Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

This is a discussion on Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6 within the Technical / Maintenance forums, part of the General Discussion category; Anyone have experience with Code P0128? Partially stuck open thermostat seems likely, or the coolant or intake temperature sensor. This ...

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    Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6


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    Anyone have experience with Code P0128?

    Partially stuck open thermostat seems likely, or the coolant or intake temperature sensor.

    This is the list of suggestions:

    * Low engine coolant level
    * Leaking or stuck open thermostat
    * Faulty cooling fan (running too much)
    * Faulty coolant temperature (ECT) sensor
    * Faulty intake air temperature (IAT) sensor
    2004 Silverado 1500 Work Truck
    4.3 Liter V6 - 5 Speed

  2. #2
    GMC RULZZ NEUMANNZZ's Avatar
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    Re: Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

    so is it low on coolant?
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
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    Old Man Mountain Swaggerwagon's Avatar
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    Re: Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

    what is your temp gauge reading..?

    if it's reading normal...them i would suspect the IAT sensor...

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    Re: Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

    Coolant is not low, and the dash gauge shows the operating temperature to be 185 F. Ambient temperature range here has been 30-40 F, warm compared to the Minnesota winter we are trying to close out (snowed again yesterday).
    2004 Silverado 1500 Work Truck
    4.3 Liter V6 - 5 Speed

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    Registered User hadfield's Avatar
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    Re: Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

    about 35 k miles ago-
    had same code on my 06 - changed temp sensor-

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    Registered User dave89iroc's Avatar
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    Re: Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

    first, replace the thermostat, this is the #1 cause for this code
    ASE Master Certified Technician

    2000 Silverado 6.0 4L80E 2wd
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    Re: Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

    Is the temp sensor the same sensor that provides the signal for the dash temp gauge? My dash temp gauge shows an operating temp of 185, which is where it has always been, following warm-up.
    2004 Silverado 1500 Work Truck
    4.3 Liter V6 - 5 Speed

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    Re: Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

    I finally got around to replacing that thermostat. It had been awhile since I had done a thermostat; it was back when a radiator had a cap and a drain. It was a bitty messy, as the coolant splashed off the frame and into a pan and onto my driveway. I got the new thermostat installed, and now my temperature gauge reads about 200 following warm-up (formerly 180). However, I am not getting any additional heat into the cab. Is it possible I am not getting coolant into the heater core? I checked the lines for a valve, but found none. Do I need to purge air? The coolant level has not gone done since I first filled it.
    2004 Silverado 1500 Work Truck
    4.3 Liter V6 - 5 Speed

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    Re: Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

    You've likely got air in the system. Sometimes it takes a heat cycle or two to get it purged but shouldn't be a major issue

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    Re: Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

    Quote Originally Posted by gmcman355 View Post
    You've likely got air in the system. Sometimes it takes a heat cycle or two to get it purged but shouldn't be a major issue
    also flush the heater core.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


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    Re: Check Engine Code PO128 (Coolant Low Temperature) 04 Silverado 4.3V6

    Quote Originally Posted by NEUMANNZZ View Post
    also flush the heater core.
    I have been driving it a couple times a day for about a week, so its seems unlikely to resolve on its own. How do I flush the heater core?
    2004 Silverado 1500 Work Truck
    4.3 Liter V6 - 5 Speed

 

 

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