Question about 2002 Audi A4

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Gas gauge is erratic (3.0 engine)

Sometimes the gauge doesn't work at all, at other times the reading is false (shows full when half empty).

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  • Richard Delahant May 11, 2010

    sounds like the fuel sending unit is bad. have it checked.

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Http://www.audiforums.com/forum/showthread.php?t=3621

That link shows you how to replace the sender. However, 99% of the time the sender can be fixed easily. When you have it out, you'll see that there's a wire that is broken (plainly visible). Use a barrel crimp connector to fix it, or use two of them to install a jumper wire between the two broken ends, and then reinstall it. You don't have to route the wire under the boom of the sender float arm - I'm not sure why Audi did that but it doesn't have to be done. Just make sure that wherever you position the wire, it doesn't interfere with anything on the sender. This is a fix about 99% of the time - this failure is common on the A4 and this is almost always the fix.

Posted on Feb 10, 2009

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j_del
  • 1586 Answers

SOURCE: Gas gauge reading is erratic.

Your sending unit is getting flaky - it's a known issue. You can repair it though, rather than buy a new sender.

Do not do this job with any more than a 1/4 tank of gas or you'll get a fuel bath in the trunk.

Here's a DIY procedure on how to do it - 99% of the time on these cars, when there's a gas gauge issue, it's the broken wire they show in the procedure. I was out of solder at the time I fixed mine, so I used barrel clamp connectors to crimp a jumper wire into place on the broken ends of the wire, and that fixed it permanently.

Here's the link:)

http://www.audiforums.com/forum/showthread.php?t=3621

Instead of replacing the sender, fix the visibly broken wire and it'll fix the failure.

Posted on Feb 10, 2009

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After a fuel fill up, the time for the fuel gauge to move from empty (E) to full (F) ranges from 2 seconds to 55 minutes depending on which operating mode the fuel gauge is in.
The default fuel gauge mode is called the anti-slosh mode. To prevent fuel gauge changes from fuel slosh (gauge instability due to changes in fuel sender readings caused by fuel moving around in the tank), the fuel gauge takes approximately 55 minutes to go from empty (E) to full (F).
The key OFF fueling mode (2 seconds to read empty [E] to full [F]) requires 3 conditions be met:
The key must be in the OFF position throughout the entire refueling of the vehicle.
At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
The instrument cluster must receive a valid key ON fuel sender reading within 1 second of the key being put into the RUN position. The key ON sample readings are considered valid if the fuel sender reading is between 15 ohms ± 2 ohms and 160 ohms ± 4 ohms.
If these conditions are not met, the fuel gauge stays in the anti-slosh mode, which results in a slow to read full (F) event.
The key ON fueling mode (approximately 90 seconds to read empty [E] to full [F]) requires 3 conditions be met:
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The key is in the RUN position.
At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
In key ON fueling mode, a 30-second timer activates after the transmission is put into the PARK (P) position (automatic transmissions). When the 30-second time has elapsed and at least 15% of the vehicle's fuel capacity has been added, the fuel gauge response time is 90 seconds to read from empty (E) to full (F). When the transmission is shifted out of PARK (P), the fuel gauge strategy reverts to the anti-slosh mode. The key on refueling mode prevents slow to read full events from happening if the customer refuels the vehicle with the key in the RUN position.
Recovery mode is incorporated into the instrument cluster strategy to recover from a missing fuel level input during a refueling event. Missing fuel level inputs result from intermittent opens in the fuel sender or its circuits. Recovery mode (empty [E] to full [F] approximately 20 minutes) is initiated when the following 2 conditions are met:
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1 Answer

Gas gauge reading is erratic.


Your sending unit is getting flaky - it's a known issue. You can repair it though, rather than buy a new sender.

Do not do this job with any more than a 1/4 tank of gas or you'll get a fuel bath in the trunk.

Here's a DIY procedure on how to do it - 99% of the time on these cars, when there's a gas gauge issue, it's the broken wire they show in the procedure. I was out of solder at the time I fixed mine, so I used barrel clamp connectors to crimp a jumper wire into place on the broken ends of the wire, and that fixed it permanently.

Here's the link:)

http://www.audiforums.com/forum/showthread.php?t=3621

Instead of replacing the sender, fix the visibly broken wire and it'll fix the failure.

Jan 20, 2009 | 2002 Audi A4

1 Answer

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hello,
the problem could be in the sending unit. this is a wired potentiometer and if you have a broken wire in the potentiometer, then that is what would happen.

you can verify this by grounding the sending unit wire to ground. you will have a full tank reading always. then use the car and see if it will still bounce and very erratic. if does not do that, then the sending unit is the problem. if it still do the erratic reading, then there are more problems.

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