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Vz tonner fuel gauge stuck on empty

Discussion in 'Electrical Wiring / Questions' started by NUGZY, Oct 19, 2019.

  1. NUGZY

    NUGZY New Member

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    Hi lads, I have a VZ tonner and the fuel gauge just sits on empty, with the alarm and low fuel warning on every start up and constant flashing bowser on dash led screen, when I turn the ign off the needle drops to resting place below the E, but will not move past the E line when key on, no matter fuel level.
    I have:
    Had the FP module out of the tank moving the sender float arm up n down with key on and still wont move.
    .Done the in dash test for gauges all gauges go to half way.
    .Replaced the sender unit ($75 wasted) as well as a full tray off job to get to the FP module
    .Tested resistance for both senders both read
    47,48 - 244 -248 ohms so all good
    Chased the wires from the tank into the cab and up to the drivers side kick panel, where the 2 sender wires go into a loom plug and come out of the joining plug on the other side as different colour wires
    (I think it was) a Tan & a Orange/blk wire from tank to the loom plug,
    And comes out the joining plug as brown/green & yellow/blk wires.
    After this I dont know where the run as the get wrapped into the main wire harness that goes through the fire wall into the engine bay.
    Im guessing maybe to ECM but not 100%.
    .Can anybody guide me as to where these wires run to from here and how the resistance signal gets back to the fuel gauge in the cluster.
    .or perhaps possible causes I could look for.
    Just trying to solve myself befor dealing with a dreaded Holden dealer.
    Any help would be greatly appreciated guys, I know these gauges are unreliable as hell but my OCD cant take the beeping and flasing anymore .
     
  2. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    Check the earth wire under the battery area, if you have good earth probably ECU or even a bad battery can cause problems.
     
  3. NUGZY

    NUGZY New Member

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    Ok cheerz Trevor, I'll check it out,
    So do the sender wires run to the ecu and then back to the gauge ?
     
  4. Fu Manchu

    Fu Manchu Well-Known Member

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    It’s not ECU related but BCM. Grab a computer set from the wreckers and see how it changes.
     
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  5. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    Sorry meant to say BCM, VZ had a big issue with fuel gauge.
     
    Last edited: Oct 20, 2019
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  6. Fu Manchu

    Fu Manchu Well-Known Member

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    Fuel gauge is operated by the BCM.
     
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  7. NUGZY

    NUGZY New Member

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    I have disconnected the battery pulled off all Earth straps around the battery 1 by 1 and cleaned all connection points with sand paper wiped them clean and refitted them.
    Have tested battery and getting a clean 12.6V sitting and 14.3V running.
    No luck gauge will still only rise to the E line.
     
  8. NUGZY

    NUGZY New Member

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    Ok thanks for clearing that up for me Fu Manchu,
    Do both of the sender wires go into the BCM and then out of the BCM to the gauge.
    Also how much should it be for a 2nd hand computer set from a wrecker, tried 1 bloke and he wanted $400 does that seem right.
    Just dont want to get stitched up.
     
  9. Fu Manchu

    Fu Manchu Well-Known Member

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    I got one for $200 for
    My Crewman. Used a wagon set. Fuel gauge would dive fast after ½ because of the bigger tank in the wagon.

    I might have a rummage through some stuff and see if I can find more specific info for you.

    At $400, that’s still cheaper than labour for a mechanic or technician to isolate the issue and then provide a new computer, then cost of syncing it to the car.

    Swapping the computers takes about 15mins.
     
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  10. VT2Commie

    VT2Commie Active Member

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    Well technically, the fuel guage is controlled by the BCM but only if the ECM tells the BCM, though single wire serial data, what the fuel gauge sender in the tank is doing. Can you extract any DTC's from it with a scantool? You will probably have P0460 logged in the ECM.
    If you have you will need to go to a dealer and get the ECM calibration updated, and configured, this is if the wires from the kick panel to the ECM are good.


    The wires you traced to the kick panel connector go to the TOP ECM connector
    You need to probe for continuity at.......
    Pin 42 for the BROWN/GREEN wire,
    Pin 25 for the BLACK/YELLOW wire,
    AT the ECM (Engine Control Module) TOP connector in the engine bay,
    to the kick panel wires you traced to.

    Pic of TOP ecm connector with pin numbers attached.

    Probe those wires, if they are good from the ECM to the kick panel plug then you are going to have to reflash the ECM at a dealer mate, which I'm pretty sure you're going to have to do.

    Oh and use a needle or a sewing pin to probe those ECM terminals. If you stuff anything other than what the size of the ECM terminal size is in there you're gonna have a f$^&ed engine harness.
    I prefer to backprobe through the seal at the top after finding the right coloured wire.

    Good luck.:)
     

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    Last edited: Nov 2, 2019
  11. NUGZY

    NUGZY New Member

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    VT2Commie
    Thanks heaps mate will check that out today
    That is the info I needed, so I know where Im going to
     
  12. VT2Commie

    VT2Commie Active Member

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    Well......
     
  13. Fu Manchu

    Fu Manchu Well-Known Member

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    Were the sender contacts in good condition? There are new pumps with faulty sender contacts. They don’t contact the sender board properly. As it swivels along, it loses contact or even no contact at all.
     
  14. NUGZY

    NUGZY New Member

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    Yeah it gets contact as Ive tested the resistance reading on the sender and chased it to the loom plug on the kick panel where the wires run to
     
  15. VT2Commie

    VT2Commie Active Member

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    ...And what about kick panel to ECM, are the wires good ?
     
  16. NUGZY

    NUGZY New Member

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    I hav'nt had a chance to chase em from there yet last time I tried I wasn't sure where they went after the kick panel loom
     
  17. VT2Commie

    VT2Commie Active Member

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  18. VT2Commie

    VT2Commie Active Member

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    .....they go to the TOP Engine Control Module plug. In the engine bay.
    NOT the Body Control Module up under the drivers kick panel.
     
    Last edited: Nov 2, 2019
  19. NUGZY

    NUGZY New Member

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    I tested for continuity from the kick panel loom to the top ecm plug (with a needle attatched to the gator clips) yesterday and couldn't get a sound from either wire, which I thought was odd,
    I could understand 1 wire with a break in the circuit but to have 2 wires that control the same component broken would be pretty dumb luck wouldn't it?
     
  20. VT2Commie

    VT2Commie Active Member

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    Yep, retest. What engine is in this VZ tonner of yours LY7 or HFV6 it'll be on the id tag at the lower left of the engine bay on the front radiator support panel.
    And also what year is it mate? as the wiring diagrams change between the 05 and 06 VZ models
     

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