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  1. #1

    Default What sensor is this?

    I'm changing the intake manifold gasket on a 1997 1500 extended cab with a Vortec 5.7ltr. While disconnecting...everything... I noticed a broken sensor. The sensor's location is drivers side, above the exhaust manifold, between the #1 & #3 spark plugs. It has a single purple wire that runs to a plug near the intake. It screws directly into the block. I'm guessing it is some sort of temperature sensor but can not find any info on it. Any ideas?

  2. #2


    A picture would help identify it. But, from what you are describing it sounds like the coolant temp sensor. At least that is where mine is located on my 5.3L

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors,
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  3. #3


    I have the same engine. I believe it is labeled as the ECM temp input/fan temp input.

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

    Check out my other mods in My Garage:

  4. #4


    I couldn't find any ECM temp but I did find a Temperature switch. This looks like it. Here's a link to the part. I just want to make sure.

  5. #5


    Yup thats it. It is one of three possible temp senders on this gen of truck. There is also one below the Thermostat housing and if the truck as an aux cooling fan one on the other side of the block in an identical place.

    LOcation of the sensor I think your talking about which is a temp gauge sender
    Click image for larger version. 

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    Location of second temp sender for ECM and such.
    Click image for larger version. 

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    Location of possible aux sender for optional aux cooling fan. I personally don't have one.
    Click image for larger version. 

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    Diagram of the aux sender
    Click image for larger version. 

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  6. #6


    Cook thanks. I was pretty sure but just wanted a second opinion. The whole cooling system was, for the lack of a better word, "jacked up". Replaced the water pump, both hoses, upper sensor (it was broken & glued together), lower sensor connection was broken & the rubber boot was slid back over it (I'd guess to hide it) & the intake manifold gasket was spewing coolant, like a natural water spring, out from between the valve cover & intake. I did a compression test to ensure that the head gaskets were good. Luckily there was a secondary temp gage installed from previous owner. It used to have a plow on it from the looks of all the horrible wiring & switches. Thanks again guys!

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