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  1. #1
    Veteran Member Four Rings earhythmic's Avatar
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    P3073 and LPFP melting pins

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    About a month ago I replaced my LPFP (only the top sender part) after being stranded in the middle of the night. When I was replacing it I noticed that the two center pins had melted the surrounding plastic of the harness connection on the pump side. Just now after barely making it home I pulled the pump harness and noticed the two middle pins are fried and melted the plastic again. I pulled codes and got P3073, intermittent fuel pump communication, so Iím guessing itís the pins again.

    Question is, why am I melting pins and what do I do about it? Could it be the pump itself is dying and drawing way more current than it should be?

    Any insight would be super appreciated


    Updated with pic:

    Last edited by earhythmic; 12-06-2018 at 02:10 PM.
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  2. #2
    Veteran Member Four Rings
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    Only thing i can think of is that your having a short or those 2 pins are positive and negative, causing current to jump but its strange your its happened twice. Have you done any kind of work on the car lately?

  3. #3
    Veteran Member Four Rings old guy's Avatar
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    That's some scary stuff.......

    No way you should be driving that car until you get it sorted out. I suspect you have a problem with the LPFP if replacing the top sender portion didn't cure the problem. Melting electrical components in you gas tank is kinda dangerous!
    A4 Motoza tuned Frankenturbo F21L / Bosch 550's / 3" MAF / TyrolSport SMIC / 034 HFC / TT 2.5" DP / Borla / Eibach ProKit / Koni Yellows / H-Sport F&R Bars / TyrolSport Brake Stiffeners / HyperShift Short Shifter / Podi
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  4. #4
    Veteran Member Four Rings earhythmic's Avatar
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    Ya, I suspect itís the pump portion itself. I found an entire assembly cheap online from a totaled car so Iíll be able to troubleshoot and keep an eye on it. No new work on the car, at least not performance-wise.

    And no worries about not driving the car, it barely holds idle so itís nit leaving the driveway
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  5. #5
    Established Member Two Rings SlvrArrw's Avatar
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    I recently had a case of a melting ground pin and dim bulb on a tail light. I tried to find a short but did not identify one. Then I remembered, as these cars age, grounding can be a problem. I ended up bypassing original ground and installing a new ground wire.
    You may new to create an additional ground wire/connection. Trace your wires and use aVOM set to continuity to find the ground.

    Sent from my SAMSUNG-SM-G935A using Tapatalk

  6. #6
    Veteran Member Four Rings earhythmic's Avatar
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    Quote Originally Posted by SlvrArrw View Post
    I recently had a case of a melting ground pin and dim bulb on a tail light. I tried to find a short but did not identify one. Then I remembered, as these cars age, grounding can be a problem. I ended up bypassing original ground and installing a new ground wire.
    You may new to create an additional ground wire/connection. Trace your wires and use aVOM set to continuity to find the ground.

    Sent from my SAMSUNG-SM-G935A using Tapatalk
    Thatís solid advice, thanks! Iíll take a multimeter to the harness in the morning.

    Does anyone know which pins are which? For the life of me I canít find a wiring diagram online.
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  7. #7
    Active Member Two Rings
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    You should buy a day pass to erwin and download the docs for your car.
    The wiring harness there should have 3 plugs (docs say there's option for a fourth, if you have an aux heater, but couldn't find it in the wiring diagram).
    One large 6 position plug goes to the J538 fuel pump control module.
    One large 4 position plug goes to the G6 transfer fuel pump.
    One smaller 6 position plug connects the G and G169 fuel level sensors to the J285 instrument cluster.

    For the J538 plug, pins 1, 2, and 3 go to pins 3, 2, and 1 on the G6 plug.
    pin 4 goes to ground, pin 5 is 12v from the fuse (panel C, ST 2, fuse 3), and pin 6 connects to the ECM

    For the G6 plug, 1, 2, and 3 go to 3, 2, 1 on the J538 plug. Pin 4 is to the same ground as the J538 pin 4. That ground in the harness eventually goes to the right rear wheel housing ground point.

    There's no identification of what is up with the three different connections between the J538 and G6. So no idea what you should expect to find on each wire. No breakdown of the G6 itself.

    But your pin 2/pin 3 on the G6 plug is wholly contained between the J538, G6, and those wires.
    2009 A4 Avant 2.0T quattro Prestige, 177k miles

  8. #8
    Established Member Four Rings Novarider's Avatar
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    Check the lpfp fuse. Someone could have swapped in a higher amp fuse then what was originally there causing it to draw more power and melt the harness. That's how some people solve fuses that keep blowing, just put a bigger one in instead.

    If you've owned it since new it's not very likely but still worth a look.
    2011 A4 Avant Prestige S-Line

  9. #9
    Veteran Member Four Rings earhythmic's Avatar
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    Took a multimeter to some things just now, but have yet to do a voltage drop test. My findings so far:

    Removed the braiding from the wiring loom on the car side, colors left to right are brown, white, red, yellow. What does that tell me? I dunno yet, but the wires in question were white and red. The cabling on the car side looks to be ok:




    Same canít be said about the cable loom on the pump side. This connects directly to the other side of those pins of the fuel sender and all four wires go directly to the pump. Notice the meltiness on the two inside wires.




    Hereís the other end of that loom, which connects directly into the pins of the pump itself:




    In that this motor has 4 leads, Iím guessing itís a bipolar stepper motor. Pulling up a generic schematic shows me:




    When testing the pins directly on the motor, Iím getting continuity on the first three pins, and the 4th pin no continuity (ground). Looking at the schematic, I feel like I shouldnít be getting continuity on three pins, but only in pairs. Would this point to an internal short in the pump causing those melted wires??
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  10. #10
    Veteran Member Four Rings earhythmic's Avatar
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    Well, replaced the pump with a known working pump. Still the same issue, stumbling at idle, on the verge of stalling after a few minutes. Looks like itís a deeper electrical issue. Ugh. Any ideas?
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  11. #11
    Established Member Two Rings
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    Bad Pcv, or leaky oil cap.


    Jeff

  12. #12
    Veteran Member Four Rings earhythmic's Avatar
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    Quote Originally Posted by JLAllroad View Post
    Bad Pcv, or leaky oil cap.


    Jeff
    Doesnít explain melted pins on the fuel pump
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  13. #13
    Veteran Member Four Rings earhythmic's Avatar
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    Oh yeah, while Iím at it, codes:

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  14. #14
    Established Member Two Rings
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    Quote Originally Posted by earhythmic View Post
    Doesnít explain melted pins on the fuel pump
    Correct, I moved on from that with the hope that your pump replacement solved your other issue.


    Jeff

  15. #15
    Active Member Two Rings
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    Did you check the state of any of the wires in the harness between the pump and controller? Did you check the controller?
    http://wiki.ross-tech.com/wiki/index.php/P3073/012403
    You have 11 faults but you post a screen cap instead of the complete text. It seems to say your G247 is broken.
    Why are you expecting things to work before you fix all your defects?
    That's a lot of electrical issues. What did you do to your car?
    2009 A4 Avant 2.0T quattro Prestige, 177k miles

  16. #16
    Veteran Member Four Rings earhythmic's Avatar
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    Quote Originally Posted by Smac770 View Post
    Did you check the state of any of the wires in the harness between the pump and controller? Did you check the controller?
    http://wiki.ross-tech.com/wiki/index.php/P3073/012403
    You have 11 faults but you post a screen cap instead of the complete text. It seems to say your G247 is broken.
    Why are you expecting things to work before you fix all your defects?
    That's a lot of electrical issues. What did you do to your car?
    You're right, rookie move, just had the screen cap handy at the time. You know how these cars are, one issue snowballs and throws a billion codes. Wires between the pump and controller are fine, pins on the controller are fine, don't exactly know how to check if that's failing internally. Here's all the codes, ignore the coolant pump and N249 ones, I always have those because of the after-runner pump TSB and DV+:

    11 Faults Found:
    18062 - Coolant Pump 2
    P261A 00 [047] - Open circuit
    Confirmed - Tested Since Memory Clear
    Freeze Frame:
    Fault Status: 00000001
    Fault Priority: 2
    Fault Frequency: 1
    Mileage: 202669 km
    Date: 2018.10.24
    Time: 22:31:24

    Engine speed: 923.50 /min
    Normed load value: 11.8 %
    Vehicle speed: 0 km/h
    Coolant temperature: 94 ∞C
    Intake air temperature: 55 ∞C
    Ambient air pressure: 1000 mbar
    Voltage terminal 30: 11.897 V
    Unlearning counter according OBD: 40
    Median injection timing: 1.645 ms
    Engine operating condition-Channel 87: Idling
    Relative load value: 14.84 %
    Engine torque: 21.4 Nm

    10063 - Fuel Pump Circuit
    P3073 00 [032] - Electrical Malfunction
    Intermittent - Not Confirmed - Tested Since Memory Clear

    2698 - Fuel Pressure Sensor (G247)
    P0192 00 [032] - Short to GND
    Intermittent - Not Confirmed - Tested Since Memory Clear
    Freeze Frame:
    Fault Status: 00000001
    Fault Priority: 2
    Fault Frequency: 13
    Mileage: 207536 km
    Date: 2018.12.06
    Time: 11:38:15

    Engine speed: 2946.50 /min
    Normed load value: 23.9 %
    Vehicle speed: 57 km/h
    Coolant temperature: 96 ∞C
    Intake air temperature: 23 ∞C
    Ambient air pressure: 1010 mbar
    Voltage terminal 30: 14.371 V
    Unlearning counter according OBD: 40
    Median injection timing: 18.704 ms
    Engine operating condition-Channel 87: Part. load
    Relative load value: 60.84 %
    Engine torque: 137.3 Nm

    5659 - Fuel Pressure Sensor (G247)
    P119A 00 [101] - Malfunction
    Not Confirmed - Tested Since Memory Clear
    Freeze Frame:
    Fault Status: 00000001
    Fault Priority: 2
    Fault Frequency: 1
    Mileage: 207532 km
    Date: 2018.12.06
    Time: 11:35:01

    Engine speed: 2384.50 /min
    Normed load value: 34.5 %
    Vehicle speed: 115 km/h
    Coolant temperature: 100 ∞C
    Intake air temperature: 24 ∞C
    Ambient air pressure: 1000 mbar
    Voltage terminal 30: 14.606 V
    Unlearning counter according OBD: 40
    Median injection timing: 3.202 ms
    Engine operating condition-Channel 87: Part. load
    Relative load value: 80.13 %
    Engine torque: 178.0 Nm

    2838 - Fuel Rail/System Pressure
    P0087 00 [100] - Too Low
    Intermittent - Not Confirmed - Tested Since Memory Clear
    Freeze Frame:
    Fault Status: 00000001
    Fault Priority: 2
    Fault Frequency: 6
    Mileage: 207512 km
    Date: 2018.12.06
    Time: 11:24:58

    Engine speed: 2792.00 /min
    Normed load value: 45.5 %
    Vehicle speed: 114 km/h
    Coolant temperature: 102 ∞C
    Intake air temperature: 23 ∞C
    Ambient air pressure: 1000 mbar
    Voltage terminal 30: 14.324 V
    Unlearning counter according OBD: 40
    Median injection timing: 4.276 ms
    Engine operating condition-Channel 87: Part. load
    Relative load value: 111.26 %
    Engine torque: 248.5 Nm

    10203 - Random/Multiple Cylinder Misfire Detected
    P0300 00 [101] - -
    Not Confirmed - Tested Since Memory Clear
    Freeze Frame:
    Fault Status: 00000001
    Fault Priority: 2
    Fault Frequency: 1
    Mileage: 207526 km
    Date: 2018.12.06
    Time: 11:32:09

    Engine speed: 2937.50 /min
    Normed load value: 33.7 %
    Vehicle speed: 118 km/h
    Coolant temperature: 100 ∞C
    Intake air temperature: 24 ∞C
    Ambient air pressure: 1000 mbar
    Voltage terminal 30: 14.465 V
    Unlearning counter according OBD: 79
    Median injection timing: 18.804 ms
    Engine operating condition-Channel 87: Part. load
    Relative load value: 81.77 %
    Engine torque: 184.9 Nm

    10591 - Cylinder 1
    P0301 00 [101] - Misfire Detected
    Not Confirmed - Tested Since Memory Clear
    Freeze Frame:
    Fault Status: 00000001
    Fault Priority: 2
    Fault Frequency: 1
    Mileage: 207535 km
    Date: 2018.12.06
    Time: 11:36:19

    Engine speed: 2500.50 /min
    Normed load value: 31.0 %
    Vehicle speed: 101 km/h
    Coolant temperature: 99 ∞C
    Intake air temperature: 25 ∞C
    Ambient air pressure: 1000 mbar
    Voltage terminal 30: 14.442 V
    Unlearning counter according OBD: 79
    Median injection timing: 23.317 ms
    Engine operating condition-Channel 87: Part. load
    Relative load value: 75.66 %
    Engine torque: 166.3 Nm

    10593 - Cylinder 3
    P0303 00 [101] - Misfire Detected
    Not Confirmed - Tested Since Memory Clear
    Freeze Frame:
    Fault Status: 00000001
    Fault Priority: 2
    Fault Frequency: 1
    Mileage: 207534 km
    Date: 2018.12.06
    Time: 11:35:51

    Engine speed: 2370.50 /min
    Normed load value: 20.4 %
    Vehicle speed: 97 km/h
    Coolant temperature: 99 ∞C
    Intake air temperature: 26 ∞C
    Ambient air pressure: 1000 mbar
    Voltage terminal 30: 14.606 V
    Unlearning counter according OBD: 79
    Median injection timing: 2.774 ms
    Engine operating condition-Channel 87: Part. load
    Relative load value: 49.20 %
    Engine torque: 110.9 Nm

    10594 - Cylinder 4
    P0304 00 [101] - Misfire Detected
    Not Confirmed - Tested Since Memory Clear
    Freeze Frame:
    Fault Status: 00000001
    Fault Priority: 2
    Fault Frequency: 1
    Mileage: 207526 km
    Date: 2018.12.06
    Time: 11:32:09

    Engine speed: 2937.50 /min
    Normed load value: 33.7 %
    Vehicle speed: 118 km/h
    Coolant temperature: 100 ∞C
    Intake air temperature: 24 ∞C
    Ambient air pressure: 1000 mbar
    Voltage terminal 30: 14.465 V
    Unlearning counter according OBD: 79
    Median injection timing: 18.804 ms
    Engine operating condition-Channel 87: Part. load
    Relative load value: 81.77 %
    Engine torque: 184.9 Nm

    10592 - Cylinder 2
    P0302 00 [101] - Misfire Detected
    Not Confirmed - Tested Since Memory Clear
    Freeze Frame:
    Fault Status: 00000001
    Fault Priority: 2
    Fault Frequency: 1
    Mileage: 207526 km
    Date: 2018.12.06
    Time: 11:32:09

    Engine speed: 2937.50 /min
    Normed load value: 33.7 %
    Vehicle speed: 118 km/h
    Coolant temperature: 100 ∞C
    Intake air temperature: 24 ∞C
    Ambient air pressure: 1000 mbar
    Voltage terminal 30: 14.465 V
    Unlearning counter according OBD: 79
    Median injection timing: 18.637 ms
    Engine operating condition-Channel 87: Part. load
    Relative load value: 81.45 %
    Engine torque: 184.2 Nm

    7663 - Boost Pressure Control Valve (N249)
    P2261 00 [108] - Mechanical Malfunction
    Intermittent - Confirmed - Tested Since Memory Clear
    Freeze Frame:
    Fault Status: 00000001
    Fault Priority: 2
    Fault Frequency: 254
    Mileage: 202673 km
    Date: 2018.10.25
    Time: 18:03:59

    Engine speed: 2379.00 /min
    Normed load value: 5.1 %
    Vehicle speed: 115 km/h
    Coolant temperature: 106 ∞C
    Intake air temperature: 26 ∞C
    Ambient air pressure: 1010 mbar
    Voltage terminal 30: 14.206 V
    Unlearning counter according OBD: 40
    Median injection timing: 0.780 ms
    Engine operating condition-Channel 87: Idling
    Relative load value: 12.94 %
    Engine torque: 17.0 Nm
    2013 Allroad - 12.18s 1/4 mile
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  17. #17
    Active Member Two Rings
    Join Date
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    Atlanta

    I think I'd start with the G247 problems. That sensor is in the high pressure rail underneath the intake manifold. Maybe it wasn't plugged back in, or the wiring got yanked and damaged? Or the sensor itself just needs to be replaced.

    After you sort that, if still problems, I'd recheck the state of those pins and then probably replace that J538 pump controller just to be sure. If the wires between the J538 and G6 are properly isolated, the grounds (pin 4 on both plugs) are good, and you know that G6 pump works, the only other component in the picture is the J538.

    After that, I'd check the LPFP duty cycle, see if it seems to be getting overdriven. I believe that's "fuel pump: specified value", which is a %, and it ranges from 43% at idle to 54% floored, for me.
    2009 A4 Avant 2.0T quattro Prestige, 177k miles

  18. #18
    Veteran Member Four Rings earhythmic's Avatar
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    So while waiting for parts to arrive, I decided to do some logging today. All logs were taken at idle.

    Requested low fuel pressure stayed at constant 649 kpa, but my actual was erratic, jumping between 615-709 kpa:


    And the high fuel pressure (looks like requested) was all over the place too. Those big dips are when the car almost stalls out:


    Wasn't able to find a way to log the actual LPFP duty cycle, but the requested stayed pretty consistent at ~30%. I'm leaning towards a failing pump control module (J538), which would explain the erratic behavior and melting of pins if the internals got fried and voltage regulator is toast.

    Anyone have any possible insight?
    Last edited by earhythmic; Yesterday at 06:01 PM.
    2013 Allroad - 12.18s 1/4 mile
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