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  1. #1
    Junior Member Two Rings
    Join Date
    Feb 27 2023
    AZ Member #
    897277
    Location
    Ohio

    S5 Fuel Gauge not working

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    Hello!

    A few weeks ago my fuel gauge did not move from low after i filled up. I took off the cover behind the backseat, unplugged and reattached the electrical connections there. It did the trick and my fuel gauge went back up. Next fillup, the gauge slowly went up and then all the way to full after a few minutes of driving.

    My gas gauge is showing E again despite just filling up and now I'm getting a fault code:

    Fuel Level sensor 2, Short circuit to ground
    Fault Code:00438
    Status: Intermittent

  2. #2
    Active Member Four Rings EuroxS4's Avatar
    Join Date
    Jan 24 2010
    AZ Member #
    53856
    My Garage
    2003 Atlas Grey A4 Avant 1.8T 6speed manual quattro,2002 GSXR 600
    Location
    Paramus,NJ USA

    If you fueled the car with it running this is normal. When fueling ignition is supposed to be off.
    VW/Audi Immobilizer removal and immobilizer adapting solutions for any and all VAG Vehicles, Odometer matching, SKC/Pin retrieval services/ Component Protection/Module Coding/Diagnosis Services and repairs.RB4/RB8 Specialist cloning and repairs. Located in Northern NJ. For inquries pm for details or contact me via Whatsapp
    Ziddy Autowerks

  3. #3
    Junior Member Two Rings
    Join Date
    Feb 27 2023
    AZ Member #
    897277
    Location
    Ohio

    Quote Originally Posted by EuroxS4 View Post
    If you fueled the car with it running this is normal. When fueling ignition is supposed to be off.
    I turn the car off every time


    Sent from my iPhone using Audizine Forum

  4. #4
    Veteran Member Four Rings
    Join Date
    Jul 16 2018
    AZ Member #
    422473
    Location
    Atlanta

    B8.0 differs from B8.5 in the fuel pump wiring. Your profile at least mentions 2013, so B8.5.

    The two fuel level sensors are wired to the instrument cluster. The sensor 1 on the in-tank pump (front right, under the rear seat bench) reads the lower 3/4 of the tank, the sensor 2 on the in-tank vent unit (left rear, under the cargo floor, have to cut the panel to access) reads the upper 3/8 of the tank. The instrument cluster transitions from sensor 2 to sensor 1 in the 6/8 to 5/8 portion of the tank.

    Each sensor is just a poteniometer swiveled by the float arm. The wiring for each sensor passes through the in-tank pump connections. For the B8.5, they are all on a single plug, the 6-pin 2x3 plug.

    To test the sensor 1 with a multimeter in resistance measurement mode, unplug the 6-pin plug and test the contact pins on the pump flange:

    – Connect multimeter (resistance test) between contacts -2- and -4-.
    • Tank empty: approx. 280 Ω.
    • Tank full: approx. 65 Ω.

    – Connect multimeter (resistance test) between contacts -2- and -6-.
    • Tank empty: approx. 60 Ω.
    • Tank full: approx. 275 Ω.

    – Connect multimeter (resistance test) between contacts -4- and -6-.
    • Sender in any position: approx. 340 Ω.
    And for sensor 2:

    – Connect multimeter (resistance test) between contacts -2- and -3-.
    • Tank empty: approx. 290 Ω.
    • Tank full: approx. 45 Ω.

    – Connect multimeter (resistance test) between contacts -2- and -5-.
    • Tank empty: approx. 50 Ω.
    • Tank full: approx. 295 Ω.

    – Connect multimeter (resistance test) between contacts -3- and -5-.
    • Sender in any position: approx. 340 Ω.
    Also note:
    To obtain an exact measurement of the resistance value for the specification “Tank full”, the fuel tank must be completely full. For this, drive for at least 500 meters after filling the tank to let air bubbles escape from the fuel tank; then add fuel again.
    It could well be a wiring issue from the 6-pin harness plug to the instrument cluster plug as well. Or an internal fault in the instrument cluster circuitry. But start with testing the sensor to see if it's obviously the issue or not obviously the issue. Could be an issue with the wiring from the sensor 2 to the backside of that plug on the in-tank flange as well.
    2009 A4 Avant 2.0T quattro Prestige, 270k miles

  5. #5
    Junior Member Two Rings
    Join Date
    Feb 27 2023
    AZ Member #
    897277
    Location
    Ohio

    Quote Originally Posted by Smac770 View Post
    B8.0 differs from B8.5 in the fuel pump wiring. Your profile at least mentions 2013, so B8.5.

    The two fuel level sensors are wired to the instrument cluster. The sensor 1 on the in-tank pump (front right, under the rear seat bench) reads the lower 3/4 of the tank, the sensor 2 on the in-tank vent unit (left rear, under the cargo floor, have to cut the panel to access) reads the upper 3/8 of the tank. The instrument cluster transitions from sensor 2 to sensor 1 in the 6/8 to 5/8 portion of the tank.

    Each sensor is just a poteniometer swiveled by the float arm. The wiring for each sensor passes through the in-tank pump connections. For the B8.5, they are all on a single plug, the 6-pin 2x3 plug.

    To test the sensor 1 with a multimeter in resistance measurement mode, unplug the 6-pin plug and test the contact pins on the pump flange:



    And for sensor 2:



    Also note:


    It could well be a wiring issue from the 6-pin harness plug to the instrument cluster plug as well. Or an internal fault in the instrument cluster circuitry. But start with testing the sensor to see if it's obviously the issue or not obviously the issue. Could be an issue with the wiring from the sensor 2 to the backside of that plug on the in-tank flange as well.
    Holy shit thanks for all god info. I’ll have to open up the tank and then test the pins shortly. I’ll keep you posted.


    Sent from my iPhone using Audizine Forum

  6. #6
    Junior Member Two Rings
    Join Date
    Feb 27 2023
    AZ Member #
    897277
    Location
    Ohio

    Quote Originally Posted by Smac770 View Post
    B8.0 differs from B8.5 in the fuel pump wiring. Your profile at least mentions 2013, so B8.5.

    The two fuel level sensors are wired to the instrument cluster. The sensor 1 on the in-tank pump (front right, under the rear seat bench) reads the lower 3/4 of the tank, the sensor 2 on the in-tank vent unit (left rear, under the cargo floor, have to cut the panel to access) reads the upper 3/8 of the tank. The instrument cluster transitions from sensor 2 to sensor 1 in the 6/8 to 5/8 portion of the tank.

    Each sensor is just a poteniometer swiveled by the float arm. The wiring for each sensor passes through the in-tank pump connections. For the B8.5, they are all on a single plug, the 6-pin 2x3 plug.

    To test the sensor 1 with a multimeter in resistance measurement mode, unplug the 6-pin plug and test the contact pins on the pump flange:



    And for sensor 2:



    Also note:


    It could well be a wiring issue from the 6-pin harness plug to the instrument cluster plug as well. Or an internal fault in the instrument cluster circuitry. But start with testing the sensor to see if it's obviously the issue or not obviously the issue. Could be an issue with the wiring from the sensor 2 to the backside of that plug on the in-tank flange as well.
    So I filled up a bit today because I was worried I may be running low and the gauge jumped and is now reading correctly. No idea why this is an intermittent issue.


    Sent from my iPhone using Audizine Forum

  7. #7
    Veteran Member Four Rings
    Join Date
    Jul 16 2018
    AZ Member #
    422473
    Location
    Atlanta

    Could be an issue with the sensor, it's just a float with a potentiometer on it. Or an issue with wiring, loose joint or corrosion or such. Too bad it's intermittent, that makes it a lot harder to sort.
    2009 A4 Avant 2.0T quattro Prestige, 270k miles

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