faciest

Hi guys. I picked up a 2005 a8 a few weeks ago that has been sat for like 6 months to a year. The fuel gauge isnt working at all. It always show empty. I tested the needle with vcds and it swept fine. The last owner said the gas gauge was working fine before. VCDS scan error code is:

Fuel supply sensor 3
open or short to plus

Let me know if u guys have any idea how to fix this? thanks in advance!

dvs_dave

Look up posts on Audi A8 fuel sender troubleshooting....

faciest

i have to bump this up. After dropping the fuel tank i found the fuel level sensor inside the tank has been stuck. i unstuck it but its still not working. Any more suggestion?

MP4.2+6.0

Hmmm, bad sensor then? Scan still show same error? No recent Audi experience though wrenching on it. D4 actually acted up on this for me in opening minutes after a fill up; I have a code. But I will just hand it to dealer on next warranty check.

Do you really have to drop tank BTW? I haven't looked in years now, but typical saddle design puts access plates under the back seats (or cargo area). Just did a fuel pump and dealt with level sender on both sides on a W211 (Merc E320) tank that way. Back seat out, plates off, remove ginormous plastic spin on ring for pumps/sensor, reach in w hand as needed.

faciest

you are right i didnt have to drop the tank but i did lol. Anyway i found a guide here to diagnose the sensor 3. I havent have time to do it yet but what does it mean if my sensor is short? or open?
here is the guide i found Audi Workshop Manuals > A8L V8-4.2L (BFM) (2004) > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Fuel Level Sensor > Component Information > Testing and Inspection > Fuel

TSHong

Short means the + wire would contact ground and short the circuit vs if the wire was somehow cut, it would be an open circuit. Typically most gauges show empty when it's an open circuit and full with a shorted circuit. Not sure if ours works that way.

faciest

ok here is the update. I was able to find out there was a open circuit with wire #2 of the connector to the fuel level sensor 3. However i do not know where it cut or open. It is the first connector i attached. Anyone has a diagram of this wire or know where its going to? I hate to remove my cluster...

1 Switched-positive connection of electric fuel pump
2 Wiring between fuel gauge sender and instrument cluster (fuel gauge)
3 Fuel gauge sender Ground (sensor Ground)
4 Electric fuel pump Ground

Here is the link where i found it
Audi Workshop Manuals > A8L V8-4.2L (BFM) (2004) > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Fuel Level Sensor > Component Information > Diagrams > Diagram Information

faciest

Lol this car is way over engineered. I was able to remove the cluster and trace both of the wire from fuel level sensor #2 and #3. At first i tried to connect those 2 wires together and was able to get the fuel gauge works, the catch is its only show 1/2 tank full while i know the tank is full. After that i sliced open the wire that i knew for sure is open circuit from sensor #3. I attached a wire and run straight to the cluster and viola it show full tank of gas which is correct!!! Why would they just make 1 fuel level sensor? 1 sensor for each side just to be more accurate fuel level reading i get it but how much more accurate can it get??
So tomorrow i have to find a way to hide the wire from the sensor 3 to cluster unless i got a wiring diagram and able to chase where its cut.