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    rkresse's Avatar
    rkresse Posts: 5, Reputation: 1
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    #1

    Mar 9, 2010, 06:40 PM
    Honda weak ground at ecu for the 02 sensor heater
    Honda civic 98 has po131 code low voltage at primary o2 sensor can't get 12 v to heater getting very weak ground signal from ecu. Could this be grounding problem?
    TxGreaseMonkey's Avatar
    TxGreaseMonkey Posts: 16,761, Reputation: 5597
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    #2

    Mar 9, 2010, 06:52 PM

    Not likely. You probably need to replace the sensor:

    https://www.askmehelpdesk.com/cars-t...tml#post223376
    rkresse's Avatar
    rkresse Posts: 5, Reputation: 1
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    #3

    Mar 9, 2010, 07:30 PM

    Sensor is new not getting 12v to the sensor heater thanks rick
    TxGreaseMonkey's Avatar
    TxGreaseMonkey Posts: 16,761, Reputation: 5597
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    #4

    Mar 10, 2010, 06:26 AM
    . Clean the main ECM ground, located on the thermostat housing, with abrasive cloth.

    . Perform K-Test on the ECM:

    The K-Test: Remove the MAP Sensor connector and turn the ignition switch to ON (Position II). Using a multimeter, check for 5 volts going between the MAP Sensor connector's reference wire (+) and ground. As you look at the connector, this is the socket on the right. Really press the black test lead into a cleaned main ECM ground on the thermostat housing. If the voltage is low, it's probably indicating ECM failure. Most failed ECMs will record a fraction of a volt. To me, the K-Test is simple, elegant, and accurate.

    The ECM (computer) is nothing more than a “power transistor,” whose job is to supply the proper voltage to a host of sensors, under constantly varying conditions. There's a real possibility the ECM is failing, if it's not providing the proper reference voltage to the Heated Oxygen Sensor. Try substituting a known good ECM.

    . Check for poor connections or loose wires at the shock tower and the ECM.

    I suspect the ECM is failing.
    rkresse's Avatar
    rkresse Posts: 5, Reputation: 1
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    #5

    Mar 10, 2010, 12:00 PM

    HI, cleaned ground wire,k-test shows .1 volt bought ecu on eBay
    Will let you know thanks Rick
    TxGreaseMonkey's Avatar
    TxGreaseMonkey Posts: 16,761, Reputation: 5597
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    #6

    Mar 10, 2010, 12:21 PM

    Yes, the ECM is fried. Here's how to swap it out:

    https://www.askmehelpdesk.com/cars-t...tml#post235038
    rkresse's Avatar
    rkresse Posts: 5, Reputation: 1
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    #7

    Mar 12, 2010, 06:25 AM

    Ecm took care of problem. Ready for smog test when get the drive cycle done thanks rick
    rkresse's Avatar
    rkresse Posts: 5, Reputation: 1
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    #8

    Mar 15, 2010, 06:25 PM

    Wow now have ck engine light no codes, good alt fuse,new ecm tested ignition switch unpugged all sensor in position 2 unreal..
    Load ak go to desert lol

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