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Thread: blue wire on ecu - what does it do?!

  1. 17th October 2013, 01:15 AM #1
    ryan1980 Guest

    blue wire on ecu - what does it do?!

    Hey guys, just got myself a discovery 2, 1998 model. 4.0 v8 manual.
    It came from an auction so i have no previous history of the car.

    There is a an aftermarket on/off switch near the steering wheel. The car sometimes stops running suddenly when i am driving it... If i turn this switch off, then on again, i can re-start the car. If i don't do this, it will not start.

    There doesnt seem to be any pattern as to when the car will stop - sometimes i can drive for an hour, sometimes only 5 minutes.

    I traced the wires from this switch. One is connected to the blue wire which goes to the ECU. The blue wire isnt cut at all - the switch wire is just soldered to it. The other wire goes to an earth.

    There is 12 volts at this blue wire unless, of course, i flip the switch to on.

    The question is... what is this blue wire for?!? and why was this switch installed?!?

    anyone got a pinout??

    Ryan
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  2. 17th October 2013, 05:52 AM #2
    ScotsD2
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    Previous owner mods

    As above can be annoying iv had on standard alarm issues with mine try and contact previous owner if you can

    You might get some info that way

    Pete
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  3. 17th October 2013, 06:58 AM #3
    OffTrack's Avatar
    OffTrack
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    Quote Originally Posted by ryan1980 View Post
    ]

    anyone got a pinout??

    Ryan
    All the wiring diagrams, pin outs and supporting information can be found on the RAVE cd. You can buy an freeraved version which can be opened with any PDF reader from the forum shop.

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  4. 17th October 2013, 01:26 PM #4
    clubagreenie's Avatar
    clubagreenie
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    Which ECU does it run to? In a D2 there's 6 I can name off the top of my head.
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  5. 17th October 2013, 03:19 PM #5
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    blue wire on ecu - what does it do?!

    Quote Originally Posted by clubagreenie View Post
    Which ECU does it run to? In a D2 there's 6 I can name off the top of my head.
    If you use your powers of deduction you should be able to narrow that down to two.
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  6. 17th October 2013, 04:56 PM #6
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    Initially I thought it could relate to the CDL mod, cutting the blue wire on the slabs ecu.

    But running a 12v source from the ecu to ground baffles me. In this case, if I understand the initial post, switching on the switch grounds the power supply (a short circuit situation?).

    I can't imagine anything in an ECU liking being shorted to earth (if the wire is post ECU and earthing it isolates whatever is on the other end) or if it's pre-ECU and grounding the wire interrupts power supply to the ECU, what that may achieve.

    **** Also 1998 is D1 not D2. ****

    Then the other issue is there's 2 coils. So what is it doing when it grounds only one?
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  7. 17th October 2013, 05:15 PM #7
    schuy1 Guest
    A quick idea, which may sound left field(or right if a left hander), as it is an after modification and commonsense states that ECU wiring should not be tampered with. How about just doing the snip and bin? For the life of me I cant see any reasoning for it, Maybe a primitive anti theft? Bin it I say and see what happens
    Cheers Scott
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  8. 17th October 2013, 05:28 PM #8
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    Quote Originally Posted by clubagreenie View Post
    Initially I thought it could relate to the CDL mod, cutting the blue wire on the slabs ecu.
    It was black and purple on mine.
    The Phantom - Oslo Blue 2001 Td5 SE.
    Half dead but will live again!

    Nina - Chawton White 2003 Td5 S
    Slowly being improved

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    You worry me sometimes Muppet!!

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  9. 17th October 2013, 05:33 PM #9
    schuy1 Guest
    Quote Originally Posted by Disco Muppet View Post
    It was black and purple on mine.
    But that was after you lost your temper with it though
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  10. 17th October 2013, 05:41 PM #10
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    Quote Originally Posted by schuy1 View Post
    But that was after you lost your temper with it though
    You should see the prop shaft I'm disassembling
    The Phantom - Oslo Blue 2001 Td5 SE.
    Half dead but will live again!

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    Slowly being improved

    Quote Originally Posted by Judo View Post
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