I went to fill up at Costco and the pump auto shut-off but my level was just above 1/2. I thought it was a fluke so I drove the car and put about 30 miles and then tried to fill up again. It shut-off at just above 1/2.

The gauge worked fine a few weeks ago and I would fill up to FULL and it would show FULL.





Is it my sending unit? If so, I was going to run a bottle or two of the Techron fuel system cleaner to see if it fixes it.

If not the sending unit. What else could it be?

The techron only helps to clean up corrosion on the stat bars, not deal with worn out swipers isntead.

So if stat bars being oxidized or corrode the probem so the swipers can not read them, may solve the problem.
Note, there are two different sending units for the vets, depending on the year, with one increasing in ohm reading as the fuel tank fills up, and the other one with ohm reading dropping as the tank is fill up instead.


Is swipers arm tips are worn out so they not longer track cleaning over the stat bars, then fuel lever sending unit will need to be replaced, which will included new float assembly with swiper arms.

Thanks for the info! For now, should I use 1 bottle of Techron per fill up? Hopefully its just oxidized...

If the Techron doesn't work, you are in for an expensive repair as the tanks need to be dropped to access the malfunctioning parts

If Techron doesn't work, I'll just fill it up and let it auto-shut off each time I drive the car. No way I'm dropping the tank for that. Yes, it's annoying to not have a working gauge but I can live with it. If I get the cracked/leaking fitting, then I would do the drop but for this, I'll leave it for now.

Car only has 14k miles on it and it worked perfectly before. I am thinking/hoping it will get fixed with a few fills of Techron over the next couple of weeks.

Is there a ground I can check for the fuel level sensor in the gas tank? I got the car up in the air so I figured to ask and see if there is a ground accessible that can be checked to make sure it is connected properly?

I was dealing with this when I bought my car. If you have it full...you can measure the resistance across the connector on top of the passenger side fuel tank. Drop the liner and there is a flap behind it. You're able to get the prongs of a multimeter on the top 2 pins of that connector.

This happened to my C6. I used Techron and it eventually worked, but only after about a year, and a bottle at almost every fill-up.
Meanwhile, I reset the trip odometer every fill-up, so I knew when to fill up again.

The last thing I wanted to do was tear apart the car to replace a $10 part.

Be careful adding a lot of Techron, may be good for the fuel sensor contacts but not so much for potential foaming in gas tank, overcleaning of fuel injector orifaces and possible oil dilution.

If the problem is a failed fuel level sensor, you should have a "service fuel system" displayed and a DTC stored. Your symptom sounds like it is the (more common) right fuel tank level sender. Get a scan tool and see if you have code P2068 or some other fuel sensor primary or secondary circuit.

See Dano's reply above. The reason the right sensor fails more often is because, at about 3/4 full of gas or less, it is no longer submerged in fuel causing it to be dry and more prone to oxidation. when you are refilling the car, the right sensor gets lubricated again and the wierdness can continue.

Search "service fuel system" on here on you can read all you want on this issue that many of us have had.

No such thing as over cleaning furl injector orifices and I doubt foaming in gas tank is a real issue. But oil dilution has been reported with excessive use of Techron. And I do keep mine topped up except on long trips.

Not everything on these cars are a bad ground…if you have a DTC for the sending units you will throw a few different trouble codes depending on which sensor and the fuel gauge defaults to E and you’ll get a “fuel level low” message which you didn’t mention…this could be a wiring issue or even a bad IPC or ECM…without some electrical diagnostic skills and a wiring diagram you will have trouble repairing this…a good factory level or equivalent aftermarket scan tool will be beneficial as you’ll be able to look at some inputs to the ECM from the senders and output test that can drive the fuel gauge from F to E !!…find an auto electric shop in your area as they deal with these things daily.

It could actually be half-full, and the pump is switching off because of a venting problem. This often manifests itself at the halfway point once fuel starts spilling over into the right tank.

Unless you're certain about the miles traveled vs. the gallons pumped, this is more likely than a gauge problem.

Try turning the fuel filler upside-down to see if you can get it to fill beyond halfway.

This is the way - I ran into this exact problem a couple of weeks ago and simply turned the pump handle to 3 o'clock from the normal 6 o'clock position and was able to completely fill my tanks.

Interesting. So just turn the nozzle from the standard 0600 position and rotate it to 0300 position?

What causes that issue?

I'll give it a shot.

Costco has more sensitive pumps and they tend to auto-shut off easier but I do not want to overfill as that can cause other issues (charcoal canister contamination).

What causes the venting problem?

What is the "Safe" Techron amount? Is it one bottle per tank, every 3,000 miles?

So is a fueling issue or you think an inaccurate fuel level issue ??…yes, you can try rotating the pump handle which is common on the C7’s or you can have an EVAP Vent Valve which is physically stuck closed and not a circuit issue.

I'm not sure at this point. I never had an issue as it would read FULL and then I went to fill-up and the pump did auto-stop and when I looked at the gauge it showed a little above 1/2 tank. So I am not sure if the tank is FULL of fuel and reading a little above 1/2 on the gauge OR the tank is actually 1/2 full and won't accept more fuel.

I will see if my scanner gets any codes on my OBD2. Is it common to have the EVAP Vent valve stuck closed? How does one check that?

Do you have a “code reader” or a bidirectional scan tool ??

Early gas station pump shut-off is relatively common. Some gas stations are touchier than others. It's easy enough to confirm: run it down to 1/4 tank and try to fill up. If it shuts off after 4 or 5 gallons, the car is only half-full.

Most actual fuel gauge malfunctions will throw a code pretty quickly. You'll see SERVICE FUEL SYSTEM on the DIC, and the gas gauge will drop to empty.