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  1. #1
    Creakin's Avatar Virgin
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    T4 CPU conflict with central locking/keys

    Hello

    I have a 2003 T4 that is used as a day van although it has been across the channel on a couple of camping trips. I bought it second hand with 300000 miles on the clock but it started first time and has factory fitted A/C, a decent sound system and came with a spare set of wheels.

    Couple of months ago the central locking and the engine immobiliser started to play up. A fortnight ago the engine stopped. VW say it might be a conflict between the instrument cluster, the CPU and the keys but they are not 100 per cent sure that a new CPU will fix it (500 plus labour plus 4 weeks for delivery).

    I am after a second or third opinion from the knowing people that might have seen this problem before and therefore might know how to fix it.

    kind regards

    Creakin

  2. #2
    S49's Avatar Privileged
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    Bend Activ8s ear sounds like his sort of thing.

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    Creakin (19th September 2018)

  4. #3
    S49's Avatar Privileged
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    Sorry, hello and welcome.

  5. #4
    Creakin's Avatar Virgin
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    Many thanks

    Creakin

  6. #5
    Activ8's Avatar Privileged
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    It reads like someones guessing. Did VW diagnose the problem with their software? What we're the codes? Keys , ECU any faults etc.. will all be identified. After that it's a process of elimination. Get the fault codes read by someone with VCDS or diagnostic kit for T4s. Hold on to your money until you narrow down the faults.

    Fuckmuppetry & Bodge Award Winner

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    regcheeseman's Avatar Privileged
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    Yeah, that makes sense. Fix a fault by replacing bits at random, and hey why not start with the most expensive single element that it also one of the most unlikely culprits.

    How many keys do you have? Any work?

    Wiring faults would be most likely.

    You say the van stopped? Was it going and then stopped or never started?

    I'd get the codes read

    And find another garage.

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    Activ8 (19th September 2018)

  9. #7
    d-9's Avatar You obviously just chat rubbish (Silver)
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    Central locking and immobiliser are two separate systems that are not linked.

    If there is an immobiliser issue, the engine will have a ‘engine start blocked by immobiliser’ code. If you don’t have comms to the ecu it may be a break in the diagnostics wire between the ecu and immobiliser box (think these are separate even on very late vans). The usual failure case is the van starts, runs for a second or two, then dies. Anything else probably isn’t immobiliser.

    Be careful with the immobiliser key pairing on those late vans, it doesn’t play nicely with vcds, I got called out to one that a mobile locksmith had bricked in a work carpark while trying to add a key. Managed to tease it back into life, but the pairing process doesn’t match the vcds documentation.

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    Activ8 (20th September 2018)

  11. #8
    regcheeseman's Avatar Privileged
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    Quote Originally Posted by d-9 View Post
    If there is an immobiliser issue, the engine will have a ‘engine start blocked by immobiliser’ code. If you don’t have comms to the ecu it may be a break in the diagnostics wire between the ecu and immobiliser box (think these are separate even on very late vans). The usual failure case is the van starts, runs for a second or two, then dies. Anything else probably isn’t immobiliser.
    Unless it is crank sensor...you could waste hours trying to fix an immo problem that isn't....guess how I know.

  12. #9
    d-9's Avatar You obviously just chat rubbish (Silver)
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    Quote Originally Posted by regcheeseman View Post
    Unless it is crank sensor...you could waste hours trying to fix an immo problem that isn't....guess how I know.
    Would expect a crank sensor to give a different code, and probably simply not start, rather than starting and dieing? I’ve seen some odd symptom on early stuff where they had two sensors, one for speed and one for tdc, but think the tdi is more modern.

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