DEAD FUEL GAUGE: Won't come back!

**Q-DawgVFR** · 09-03-2009 07:30 AM

OK, so I've read through some threads, but no answers that I need were found. Here's the story:

Car sat parked for about three weeks with limited driving before that. (Was working a lot leading into my vacation.)

Went to start car to drive to Calgary, and the battery was low. It had enough juice to try starting, but just not quite enough. It's failed attempt to start threw a trouble code.

I was in danger of missing appointment with locksmith in the city, so I hooked up jumper cables from 4Runner to the S4 and let it run for a few minutes. I could not find a good ground point to hook the booster cable to, so I just did + to +, - to - on the battery terminals. I did not want to use the fuel rails in case of leaks / sparks, and just couldn't find any other easy way to do it.

Car started up after a few minutes charging, but was running really rough and the fuel gauge was dead. Oh no! So I let the car run a couple minutes, then shut off the ignition. I used my cheap-o OBD2 code reader to clear the code (didn't have time to mess with VAG-Com, which I'm a total newb with) and re-started the car. No code, no rough idle, and fuel gauge working again. Whew!

So I drive the 45 minutes to Calgary and meet with the locksmith who is going to cut my new transponder keys for me. He takes all my keys / remotes and I head back into the Tim Horton's nearby to enjoy coffee and breakfast with my wife and kids, leaving him to do his craft un-interrupted. We go to the store next door and I pop out again when I notice the car and his locksmith van is running. He must be done and ready to go.

I head over there and he tells me that he had to boost the car with his booster pack because the car went dead while he sat around with the ignition switched on. He had not turned off the radio or A/C to conserve power while he tried un-successfully to program the keys. He says he left the car running to charge up and that he will only charge half his rate because he could not get the keys programmed in. No problem, I tell him I am on the way to dealer to get keys programmed anyway and radio code looked up for the RNS-E swap that previous owner did.

We part ways, and I notice the fuel gauge is dead again. Not too worried yet, but after I get to the dealership, I cycle the car off and back on. The fuel gauge does not come back! I have the car keys programmed and code looked up, but skipped having Audi dealer look at fuel gauge issue because they said they would need the car for another hour or two and I did not want to wait with my family that long. I figure I can just reset the code when I get home or it will be easy fix with VAG-Com. Not so.

I get home and try the cheap-O OBD2 code scanner to reset the trouble code. No luck and no working fuel gauge. I did a scan (first time ever,) using the VAG-Com and found a code or two. Hard to remember what it said (this happened almost a month ago now) but something about "fuel gauge: implausible signal" was in there.

I read some threads and it sounds like the fuel gauge should have just come back when battery charged up normal again. No one seems to have had theirs not come back, so I have no idea what to do next.

Dealer is very inconvenient to get to without booking well in advance, and I would prefer to fix this myself if I can get some help from you folks.

I have FSM (will have to install the software to read it; will see if that gives me any ideas) and I also have the VAG-Com, but I am very inexperienced in using it. Willing to learn, but do not have tons of time to play around getting to learn it just yet. If someone can offer me some step-by-step on what specifically to try looking at, then I can fake my way through it.

Someone in another thread mentioned something about pulling, then replacing the fuse to the instrument cluster: will reset the cluster? I was thinking of trying this first, as it is really easy to do.

Any help you folks can lend would be appreciated; thanks!

**dfresh000** · 09-03-2009 08:16 AM

sounds like faulty fuel sensor. had mine go 2yrs ago with same symptoms you're reporting. have it looked at & replaced if need be.. GL

**Condo** · 09-03-2009 08:45 AM

Just give it time. The fuel gauge will come back. This happens sometimes when the battery gets low or disconnected.

**Q-DawgVFR** · 09-03-2009 08:54 AM

Originally Posted by Condo

Just give it time. The fuel gauge will come back. This happens sometimes when the battery gets low or disconnected.

I know that. I've waited a month and it hasn't fixed itself.

No matter how much I will it to fix itself, my Jedi mind powers are not gonna work on this one!

It needs some real fix'n, I'm afraid.

Anyone have any ideas how boosting the car or low battery could have permanently done this? I'm thinking that the two are related, since the gauge was working fine until the day that the locksmith boosted the car.

**infernocl** · 09-03-2009 11:06 AM

try pulling the instrument cluster fuse and put it back in

**downhillracer** · 09-03-2009 11:14 AM

have you tried disconnecting the battery for like 15 min. then hooking it back up... It will let all the modules die completely and they will all..."reset" so to speak. i would try that. Thats worked for me many times when thinks go wacky.

If that doesn't work your fuel level sender is probably a bad

**reapersa4** · 09-03-2009 11:25 AM

funny you post this! It is sort of related, the fuel light comes on on my dash, but I still have half a tank of fuel! any thoughts on this?

sorry to thread jack.

**jbrown7815** · 09-03-2009 11:33 AM

or related to mine, My guage just stops a little under half a tank, so I never know when I'm low on gas, unless I watch mileage.

**F16HTON** · 09-03-2009 11:47 AM

Fuel sending unit may be going bad, there are two of them so it take a little skill to figure out what to replace.

You will have to put a multimeter to the wiring and see what resistance you get across the sender. The good thing is that you can do this without opening the tank and checking the plug.

**Q-DawgVFR** · 09-03-2009 01:52 PM

SUCCESS!

Thanks for the suggestion to pull the instrument cluster fuse to reset the panel.

It did the trick.

I pulled the fuse and left it out for half a minute for everything to go completely dead, then re-inserted it.

Turned the key and the fuel gauge needle swept up to the present fuel level (about half a tank, which seems pretty much where I remember it to be.)

Gotta love the easy fixes! I was worried that it was going to cost me more to fix the fuel gauge than the amount I saved by getting my keys cut by the locksmith. Not so.

Thanks, people!