WRX Coolant Sensor
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This is a discussion on WRX Coolant Sensor within the Everyday Impreza Talk forums, part of the Community - Meet other Enthusiasts category; Hi Everyone, I replaced the coolant temp sensor on my 2003 wrx. the codes that were showing were a 420 ...

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    WRX Coolant Sensor

    Hi Everyone,

    I replaced the coolant temp sensor on my 2003 wrx. the codes that were showing were a 420 and a 117 code. i decided to take on the sensor first since i had the cads replaced (not stock...my mistake). so i put on the coolant temp sensor and immediately noticed that the temp guage was showing Hot. i burped the system and the same thing. took it to a shop and they ran it through a coolant system diagnostic to tell me that the care was not overheating at all and that it was a false reading. does the temp sensor need to be stock? i got it from an auto parts store. it doesn't make a whole lot of sense to me.

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    He simply abides. SD_GR's Avatar
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    What are cads?

    Does the new sensor differ in impedance to the old sensor?

    Are the leads reversible or is the harness directional to prevent that?
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
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    Quote Originally Posted by SD_GR View Post
    What are cads?

    Does the new sensor differ in impedance to the old sensor?

    im not sure. how could i tell?

    Are the leads reversible or is the harness directional to prevent that?
    the harness is directional

    im sorry i meant CATS not cads.

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    He simply abides. SD_GR's Avatar
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    WRX Coolant Sensor

    If you are certain the car is NOT overheating then and only then consider seeing what happens when the harness is left disconnected. This could show whether the fault is with the sensor or the harness.

    I was also interested in any readings using a multimeter set to impedance across the old vs the new sensor.
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

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    Quote Originally Posted by SD_GR View Post
    If you are certain the car is NOT overheating then and only then consider seeing what happens when the harness is left disconnected. This could show whether the fault is with the sensor or the harness.

    I was also interested in any readings using a multimeter set to impedance across the old vs the new sensor.
    I will check that out. thanks for all the input.

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    Quote Originally Posted by timmyflash View Post
    I will check that out. thanks for all the input.
    I spoke with the mechanic on the phone. he's telling me that it's probably something wrong with the coolant temp senor. he said all internal temps checked out normal and that it could only be between the sensor and/or the plug being the reason it's showing hot. i did not buy the sensor stock. should i have bought a stock sensor?

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    He simply abides. SD_GR's Avatar
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    Quote Originally Posted by timmyflash View Post
    I spoke with the mechanic on the phone. he's telling me that it's probably something wrong with the coolant temp senor. he said all internal temps checked out normal and that it could only be between the sensor and/or the plug being the reason it's showing hot. i did not buy the sensor stock. should i have bought a stock sensor?
    I can't tell from the information given because we don't have a known good stock sensor to measure and compare to the one you've bought. I don't disagree that it could be the wiring either; there's no way given what we know so far to eliminate one over the other.
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

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