Brozee

Hey guys,

For the past year or so my 2005 A8 was having issues with the fuel gauge. Long story short, I tried diagnosing it myself and one day was unable to contact the Instrument cluster portion in VCDS. All other modules worked without any issues, but anytime I tried getting into it it would say it was unreachable. My reason for wanting to diagnose under that module is that the fuel senders are under that menu. Instrument cluster is also the menu that resets the service light and interval timing. So for the past year it has been saying "Service!". I scoured the forums and didn't find anyone else ever getting locked out or not being able to access a module unless that module was dead. I know for sure that the module was functioning properly outside of letting me gain diagnostic access. I was able to find one thread that was either from the UK or from Australia in which one user wasn't allowed access to a module he otherwise was able to in the past. The solution recommended was fully reset or cycle the car's computer.

Fix:
After changing the oil myself in the car (PITA by the way), I decided to pull the leads off the battery in the trunk to reset the cars computers and reset/clear anything that could have been wrong. Sure enough, the car went dead after pulling the leads, I reconnected and the car turned on no problem after leaving it disconnected for about a minute or so. I then went through the MMI, and all settings were as I left them before disconnecting the battery. Batter meter was still shown in MMI, all other settings/tweaks I did was still intact including the seat belt chime delete, etc. Only thing I had to reset was the convenience opening of the windows, which is reset by rolling up the windows, holding up on the window switch til you hear a click on that window, and the option is enabled again. I connected VCDS, and was able to gain access to the instrument cluster once again! Also was able to reset the service light. Still haven't been able to figure out why the gas gauge isn't reading a full tank (stays at 75%, slowly rises to full if at all, over time).

Wanted to pass this along to anyone in the event they ever experience the same issues that I had! Hope it helps

jakematic

Kudos for sharing that.
That's exactly what is required in most cases when a module gets 'confused', usually when the CAN bus gets clogged with DTC messages.

For future readers, sometimes you need to touch the +/- leads and turn the key on to completely drain residual voltages.

Mister Bally

Sound similar to the three mirrors on my car always darkening to near black whenever powering the ignition this past winter. Made night driving difficult. VCDS showed no codes. Finally did the old "hard reset" by disconnecting the battery and all has been well ever since.

Panelhead

I had a new "Smart" key programmed to the car last Friday. My mirrors turn dark, the rear sunscreen comes up on starting, and the drivers door does not unlock when the car is shut off.
The door lock is fixed by turning automatic lock to off on the MMI. I do not know how to turn off the sunscreen and mirrors. My try a hard reset when I get back home this week.

MP4.2+6.0

Rear shade on start up should just be an MMI setting change.

aTOMic

^^ What he said, plus the car associates many settings with each key individually, just like the seat memory changes the seat depending on whose key unlocks the car - most cars do this nowadays. But our cars recall personalized settings for HVAC, park sensor volume, interior lighting scheme, and probably rear sunshade - and change them for each driver!

I just hate the tedious job of having to lift my arm, look at the rearview mirror, maybe move it - by HAND - a couple millimeters. I mean what was Audi THINKING?! The S-class had auto adujst mirrors in 2004 IIRC! Sheesh!

(I still think it's borderline overkill but then again it's almost a safety feature since it sets the mirror for you in case you forget).

While the A8 is having the front end refreshed*, I've been driving my Parents' Toiletta Highlander "Limited" (pretty sure the name refers to its capabilities) and EVERYTHING sucks about that thing! Even the power seats, which are supposed to be a luxury feature, are S O O O S L O W and they really don't move far at all. Got a V6, can't get out of its own way, AND gets worse mileage than the A8L! I tried driving a slowly as I could stand without impeding traffic and got 17.7 MPG on the last tiny tankful! 16 gallon tank means I have to fill up twice as often as the Audi. A/C cant maintain a temp, it seems to only have two settings: over 74 (=too hot) or below 74 at which time it goes into recirc and fan noise is deafening. I really think the climate control is primitive.

Oh well, we're calling it "Audi Appreciation Month!"

*new brakes, axles, control arms, TREs, and it's taking me a month, between all the extra stuff that keeps me from doing the work.