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Thread: ECU broken ? or not...

  1. #1
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    ECU broken ? or not...

    Hi , need some urgent help!

    My xj6 3,2 1991 doesent start, the fuel pump relay is not energized on the coil from ECM. Wiring checked.
    Is this defenitely a broken ECM or would it be the same result if crank position sensor is broken?

    Engine cranks
    Fuel pump is running when relay is forced
    No fault codes
    No spark
    Inertia switch ok

    ECM part nr is DBC6472 , if you have one to sell im interested to buy one.

    Best regards/willep

  2. #2
    Senior Member rchiv's Avatar
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    Hi Willep, Welcome to the forum.

    What code reader are you using. If it was an ECU fault then you would have a code of some sort or a failure to read ECM. It looks like a security immobilizer problem rather than an ECU fault.
    As the engine turns over it eliminates the Inertia switch.
    Crank sensor would not stop the fuel pump or spark. But would have a code as well.


    Roger
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  3. #3
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    Hi,

    Has anybody recently deleted the codes or has this just appeared out of the blue?
    Grumpy Old Git
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  4. #4
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    My xj6 3,2 1991 doesent start, the fuel pump relay is not energized on the coil from ECM. Wiring checked.
    Is this defenitely a broken ECM or would it be the same result if crank position sensor is broken?
    bad ECM could definitely brick the starting process
    When cranking does the tachometer "pulse? I was told this indicates the CPS is outputting signal.
    I believe the 2 second running of the fuel pump is controlled by the ECU and may indicate it is bad.
    Check all grounds and insure voltage is getting to the ECU module...
    Fuel pump is running when relay is forced
    I assume you car just "died"-no spark--- one day... yeah that sounds like and electronic failure, they are sudden and with no warning...... make some of those prelim checks of voltages and grounds.... try and get a sub ECU as it is good to have a spare.
    ALSO just unplug and replace all the ignition connectors... and LOOK... do they look reasonably clean... is there decent "friction" when reconnecting the connector?
    Good cleaners are WD40 ELECTRICAL CONTACT CLEANER wont hurt any plastic parts...and
    Deoxit GOLD G5

    Have a clean and ground and voltage check.. if still nogo... get that spare ECU

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