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A8 / S8 (D3 Platform) Discussion Discussion forum for the D3 Audi A8 produced from 2003-2010 and Audi S8 produced from 2006-2010

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Old 06-28-2014, 01:55 PM   #1
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Default Faulty fuel gauge audi a8 4.2tdi

The following situation occured with my audi a8.

The fuel gauge shows empty, while the tank is full. No fault codes.

I already took the 4 sensors out of the tank, and the resistance of every sensor looks ok. Upper sensors are 70-157ohm. the lower sensors are 50-300ohm.

There are no fault codes. Fuel gauge just shows empty.

When doing the analog test with vcds the fuel gauge meter works.

The car has a diesel engine, but the gasonline version uses the same gauge senders.

Anyone experienced this problem?


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Old 06-30-2014, 07:17 PM   #2
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Have the same issue with my 4.2 but it somewhat works. No codes and the sensors all read fine. Now I'm locked out and can't access the instruments section of vcds. I think I have to disconnect the battery to fix it.
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Old 07-01-2014, 01:18 PM   #3
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Yes I've had the same thing on my W12, although mine doesn't show empty all the time, it will only show empty if the tank is more than half full, half full and under it reads but is a bit out, I've run out a few times with it showing just above reserve. It's apparently the wiring loom, I've read it somewhere on here that it's basically a bad/broken wire and my garage also did some research and has done another with the same problem. Trouble is replacing the whole loom is a big job, they are seeing if it can be 'fixed' where you don't have to replace the whole loom but just the one wire instead.
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Old 07-07-2014, 12:18 PM   #4
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Thanks for the answers!

I just checked all sensors again. The lower sensors have a resistance from 50 to 1000 Ohm. I mentioned 50 to 300 Ohm in the first post, but that is not correct. OEM value is 50 to 1000.

I also checked the wires. There are 5 wires that go directly from the cockpit to the sensors. 1 wire is the supply voltage that goes to all sensors. The other 4 wires are the "returning" ones from the fuel sensors to the cockpit. These wires are not open or short to plus. To make sure I made 5 new wires running through the trunk straight to the cockpit. This makes no difference. I strongly suspect the cluster itself. It will be tested this week by a rebuilding company. To be continued...
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Old 07-07-2014, 12:23 PM   #5
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Default Thanks for the update here

I don't have anything to add, but appreciate the info. if it ever comes up for me or others. Cluster failure possibility rather than the usual sensors is a new twist.
Current #1: '06 D3 A8L W12 brilliant black w/ amaretto; 4 seat setup, CPO; modestly lowered, H&R 20mm rear and 12mm front DRs with 275/35 on OEM polished + forged 20's; S8 sway bars (see: rear bar and gen'l D3 bar info and front bar); tweaked 385mm front factory brake mod and matching rear brake mod; matching C6 A6 back headrests (better rear view: headrest tweak); owner installed AMI retrofit with part number details here.
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helpful cross reference to a C6 post with MMI and other TSB's that also cover D3 A8's.

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Old 07-21-2014, 06:56 AM   #6
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Instrument cluster was send to two different rebuilders, both were not able to diagnose/test it properly.

I'm now looking for a used one. I assume I have to go to the dealer to have it installed. This is not a VCDS Job. What info do I need from the donor car?

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Old 07-21-2014, 07:17 AM   #7
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Instrument cluster has Component Protection and it has to be removed by a dealer. Problem is with the millage. It can't be adjusted (except if it is a brand new cluster). So donor car must be same as yours and millage on it should be close to your millage. Be aware that it is also recorded in the engine computer, so cheating is not advisable.
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Old 07-21-2014, 07:17 AM
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