Gas gauge off after replacing battery

The fuel gauge does not go to full - shows 3/4 a tank after fueling. I replaced the battery without a full tank of gas, and that is probably what caused this. I've been all over my owners manual, and cannot figure out how to reset this without filling up and pulling out the battery. Is there a trick, or the best option is just fuel up and pull the battery?

C4 or Turbo? If so the isolated part of the tank is inferred after it gets below a certain level. How much gas was in the tank when you replaced the battery? You might try filling it and disconnecting the battery. I think I read that you have to see dealer to reset it. They drain the tank add a known amount then reset the gauge. There may be other ways to reset. Did you try a search on Renntech.org? If you aren't a member you might want to join. Then you can see TSBs, manuals etc... Below is from a thread on Renntech http://www.renntech.org/forums/topic..._1#entry191875 "Calibrating fuel level sensor system 1. Disconnect the battery and cover terminal or battery. 2. Remove cap over the fuel level sensor system. 3. Remove fuel level sensor. Removing and installing fuel pump. 4. Using a fuel extractor, completely drain the fuel tank through the fuel level sensor opening. 5. −Make sure that the two recesses on the left and right−hand sides of the tank are emptied completely.− 6. Reinstall the fuel level sensor and, with "ignition off", fill the tank with exactly 28 liters of fuel. 7. Perform tank calibration with the Porsche System Tester 2: - Select vehicle type (911 Carrera) - Select control modules - Select instrument cluster - Select menu item "Tank calibration" - Confirm calibration 8. The fuel level sensor system has now been calibrated."

C4 (2001) I'll give the fill/disconnect a try tomorrow. I was hoping for an easier way, but have wrench and the radio code handy. (Had a subscription to renntech a while back, but had problems with the login. Never did get it sorted.)

My fuel gauge also does not display properly. It reads about 7/8 full when it has been filled to the brim, and about 1/8 when totally empty. This resulted after an engine, computer and instrument panel swap. I have a '99 C4. The instrument panel had to be changed so the cruise control would work with the 3.6 engine and ECU. Before the swap, the fuel gauge was operating properly. So, I will be interested to hear if the reset procedure posted earlier will fix the problem. Keep us posted!

Quotes source post: 8859330

This is crazy, isn't it? It's hard to beleive this much work has to be performed to calibrate the fuel gauge after a simple act of changing the battery........ How about those folks who take the battery out of their cars for winter storage? Has this been an issue for you folks?

As long as you have more then (1/2?) tank there will be no problem. If you pull the battery when the level is below the *"split" you will lose calibration. *"...two recesses on the left and right−hand sides of the tank..." NOTE: This only on four wheel drive cars, Turbo, C4, they have a saddle tank to clear the front diff and still have enough fuel.

If you DIY make sure to place the pickup hoses back to the original positions or you may allow them to foul the fuel filler door flap. If that happens you will not be able to put more than a cup full of fuel in the tank at a time. Do a search there is info and pics floating around Rennlist I think There is a TSB for tying them back when they get out of position on their own. Access to the fuel pump/sending unit is under the battery on C2 and here on C4

Thank you for the picture. Did not realize the fuel pump was that easy to get at. Getting to be that time of life where I should update the fuel filter too. More homework for the weekend.

heelix, have you tried this procedure yet?

This part of the procedure is probably dealer only. "7. Perform tank calibration with the Porsche System Tester 2: - Select vehicle type (911 Carrera) - Select control modules - Select instrument cluster - Select menu item "Tank calibration" - Confirm calibration"

That cover is access to the sender, pump, (attached to the bottom of the tank by ~1/2 turn click into socket) and a spagetti of hoses. If your car has a filter (pre 2001 - 2? not sure) it will be up in the tunnel under the car pain to change.

Quotes source post: 8863176

Frank, do you know if the Durametric product will do the same as the Porsche System Tester? Seems hardly worthwhile doing this as a DIY if you have to take it to the dealer for the last step, where who knows what they will charge you.

Fueling and 'rebooting' the car overnight with the battery out seems to have done the trick.

Did not even think to hook my Durametric cable up and see if fuel calibration was an option.

No, Durametric does not have this option. Only a PST2 or PIWIS can do this calibration. FWIW, on my 1999 car, calibration is no longer possible - the level sender is too old, and the PST2 reports that the calibration margins are too far out of spec.

heelix, that is good news. Did you fill the car drive home and then disconnect the battery or disconnect the battery and then fill from jugs? Rickker, looks like there may be a way around the dealer procedure, at least in some cases. logray, does that mean that a new sender would be required to calibrate yours, or that you are SOL no matter what?

new sender for me should fix the problem

I fueled first, then pulled the battery. I also let it sit overnight, to fully clear any battery backup. Not sure I needed to, but it looks like a full tank shows just under full. Will pull out the diagnostic cable this weekend to see how much fuel it really thinks she has with the tank topped this weekend when I fly home.

Quotes source post: 8863399

heelix, can you elaborate on what exactly you did? Did you disconnect the battery and then filled the tank, then connected it again? Not sure what you mean by 'rebooting', I know what it means with a PC, but not a P-car.

ask an important question and posters never get back with an answer. That really pisses me off with these boards. He needs a 're boot'. A leather boot in the **** of his pants. Preferably when he is wearing them. lol.

Post 18 is his reboot procedure. I take it to mean he disconnected the battery to "reboot" the system.

TL;DR - but you simply need to fill the car completely. The car estimates range once the tank in a C4 gets below a quarter full (it's a saddle tank, and the sender only knows the fuel level for its side of the tank). If you disconnect the battery when the car is in this state, the range estimate data is lost and the fuel gauge will be incorrect until you fill the tank again. You do not need to re-boot the car, disconnect the battery again, or anything else.