EEC trouble :(

Discussion in 'Fox 5.0 Mustang Tech' started by Camman, Dec 6, 2003.


  1. Camman

    Camman Founding Member

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    My check engine is always on in my 89 gt. I thought it was the computer circuit being fried, but I just put a new comp in and the c/e light is still on constantly. I can not pull codes from the damn thing, when I plug in my tester the light just stays constantly on, doesnt pull any codes. What should I look for? Anything else that would cause the c/e light to stay on besides the computer? Thanks
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  2. custom90GT

    custom90GT Founding Member

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    Are you sure your tester is good? Replacing the computer doesn't get rid of whats causing the code (at least most of the time). have you tried to pull codes using the check engine light method?
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  3. Camman

    Camman Founding Member

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    yes I have tried the check engine light method. The reason I replaced the computer is because I thought the sto circuit was bad, apperantly its not, so what else could I check for? Woulc a bad o2 ground cause this?
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  4. custom90GT

    custom90GT Founding Member

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    Well it might be a bad computer ground somewhere (I've heard it can throw codes, but have never had to deal with it personally). How does the car run?
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  5. Camman

    Camman Founding Member

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    The car runs strong, but I can tell there is a sensor out, maybe the ect, but I need to be able to pull codes. I checked the grounds on the main harness, they look good, so is there a list or something somewhere, troubleshooting? I dont know what to do, I really would like my computer to work like its supposed to :). Thanks for the help
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  6. custom90GT

    custom90GT Founding Member

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    hummmm, does it run rich or anything like that? Did you use a voltmeter to test the grounds and even power to the eec sensor? Look for a Tmoss wiring diagram for the EEC if you dont have one already (I dont have it here at work). Also, you might check the ground/power on the O2 sensors. I still dont understand why it wont give you codes. You didn't convert from an auto to a five speed and switch computers did you? Is the light on ALL the time or is it when you rev it up or something?
    Come on guys, lets help this guy out.
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  7. IndyBlk5.0

    IndyBlk5.0 New Member

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    sometimes the tester doesnt work until you turn off your car, did you try plugging it in with your car off, and thens tarting it ? I know it wouldnt work on my car unless i did that.
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  8. Mike86Stang

    Mike86Stang Advanced Member

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    I have the same problem...pin 46 (signal return wire) is shorted out most likely...easiest thing to do is ground it out & you can pull codes & the EEC will actually read the sensor but you will still have a CEL on....(check engine light).

    Only solution is to trace the short & repair it, or replace the whole wire (tis a real B*t#$)
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  9. Camman

    Camman Founding Member

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    I ran a new wire for pin 46, and it worked!! Thanks!!
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  10. tmoss

    tmoss Gettin Wired Founding Member

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    MSTANG - is this a common problem? You hit that one on the nose right out of the gate. How did you determine your wire #46 was grounded? use an ohmeter or what?
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