B5 1.8t Top 10 Causes For No Spark
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  1. #1
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    B5 1.8t Top 10 Causes For No Spark

    I didn't see a list anywhere, so thought I'd start one. This list is for likely causes for a b5 when engine is turning over, getting fuel but no spark to any plugs.
    I read through many posts and found a bunch of random suggestions and I've gone through them all to get some ideas.

    1. Battery - Weak battery, Poor connections
    2. Fuse - Bad fuse (29, which others?)
    3. ICM - Bad part or poor connection? N/A for 2001+?
    4. ECM - Bad ECM or poor connections, or wet?
    5. ECM Ground - Poor ground near ECM?
    6. CCM - Faulty CCM, poor connection or wet?
    7. CCM - Harness bad junction/splice?
    8. CCM Ground - Poor ground DS floor or near firewall?
    9. TCM - Could this be an issue?
    10. Immobilizer?


    I'm also having this issue myself right now.
    Car was parked and with no battery in it for a long time due to work needed.
    Installed a new k04 and did an oil change.
    Had water intrusion issues a few times, clogged drains in battery compartment.
    Removed CCM, it was dry and everything looked perfectly clean.
    Carpet did get wet on drivers side a few times, but has been dry for a long time and looks fine.
    Carpet has been soaked many times on passenger side, TCM housing was still full of water when I removed it.
    Checked the ECM. Looked perfect and doesn't look like it could ever get wet with that large hole for the wires to go inside the car.
    Disconnected fuel line and turned the engine over. Plenty of fuel is coming out.
    Pulled coils, inserted known good plugs, rested them on the valve cover and turned key. Did this at night, definitely no spark.



    Any thoughts or suggestions? Items to add to my list or suggestions for me?

    Thanks,
    Ed
    Last edited by n2nsanity; 05-26-2012 at 10:50 AM.

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  3. #2
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    Some updates...

    Disconnected battery and discharged system
    All fuses look good. Replaced ECM related ones anyway as suggested somewhere else.
    Everything appears connected
    It's a 2001 and doesn't have an ICM
    CCM seems ok. Lights, Doors, Windows, Mirrors all work

    Another attempt to start. Still no spark
    PRND321 All lit up on HUD
    Shifter Brake Indicater lit up
    Shifter Gear Indicator lit up
    No changes on HUD when shifting
    Scanned codes
    p0171
    p0685
    p0884

    Erased All Codes

    Scanned again
    p0685

    Removed TCM
    p0600
    Attempted start, Still no spark
    No Gear lights on HUD
    No Shifter Brake Light
    No Shifter Gear Light


    So amazingly the TCM seems to be at least partially working. Replacing it regardless.
    Could a bad TCM be related?
    Could corroded wires near the TCM be an issue?
    Could it be the crank sensor? I haven't touched it, but I'm pretty sure that would cause no spark.

  4. #3
    Moderate Moderator Steve in Chicago's Avatar
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    Check fuse 29 (20 amp) to see if it's good. That's the fuse protecting the circuit providing voltage to the coils. Then check pin 1 at any of the coil harness connectors for voltage.

    http://www.audigeeks.com/images/tech...tronic_ATW.jpg

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    Checked all of my fuses. Even replaced some that weren't blown.
    According to my diagram, #29 is ECM fuse 15amp
    Fuse cards are missing of course...

    Check for voltage at coil with key turned off, on, or while attempting to start?
    And is pin 1 towards the rounded end or the square end?

    Anything to add to my list or the order of it?

  6. #5
    Moderate Moderator Steve in Chicago's Avatar
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    Quote Originally Posted by n2nsanity View Post
    Check for voltage at coil with key turned off, on, or while attempting to start?
    I'm not exactly sure. That circuit needs to be live for the coils to function. I would guess it may be dead when the ignition is off. May or may not be live with the ignition simply switched on. But it'd definitely need to be live when cranking and running.

  7. #6
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    You should see battery voltage at the coils with the key on. ECM sends ground signal to fire coils.

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    So I got a new scanner specific to vw/audi
    It was only a few $ more than my old generic one, it's sooo much better.

    Here are the codes I'm getting.

    Engine
    -------
    P0685
    17069-035
    KWP1281
    ECM Power Relay Control Circuit (J271) Open

    P1602
    18010-163
    KWP1281
    Power Supply Terminal 30
    Voltage too low

    Trans
    --------
    P1750
    18158-035
    KWP1281
    Supply voltage too low


    Battery is good. Had it tested and on the slow charger over night.

    My new TCU doesn't seem to be working now. It's been disconnected as well as the battery since the last time I've messed with any of this. I'm hoping it's just corrosion on the connector causing this.

    Anyone familiar with these codes?

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