Fuel gauge “EMPTY” when full
 

Maybe some of you guys have a answer for this one.

My my fuel gauge goes to empty occasionally. This can happen anytime and anywhere for me.
Driving along with as much as 3/4 tank and look at the gauges and tank is reading empty. Gauge is maxed at the bottom of the reader, switching to the DIC to check the mileage left on the tank and nothing but ———- .

when I had my C6 Z I learned that most problems could be cleared by removing a battery lead from the battery for 5 mininutes and all is good to go. The same with this problem but because it has happened 8 to ten times since 2015:I thought I would ask you knowledgeable guys.

If if I take it to the dealer with it working they will not do anything. I don’t think it’s mechanical because it resets when I pull the battery positive off. is there a reset switch to the entire electronic system without taking off the positive connection?

thanks to those who chime in positive.

Steve

Greetings.

Generally what happens is the fuel level potentiometer and the fuel level arm contacts get a build up on them.
This build up occurs most on the areas of the potentiometer that are least exercised.

In other words if you keep the car full or over half full most of the time the arm on the fuel level potentiometer will never "sweep" through its full arch and swipe (polish/clean) the contacts.

A large percentage of these issues have been cured by the following process.

Drive the car until you are fairly certain it has 1/4 to less than 1/2 tank full.
Put 20-24 ounces of Techron fuel system cleaner in the tank and fill the car to at least 3/4 full but shy of completely full.
Drive the car as you normally would.

Sometimes I have had to do this twice over a couple of weeks to get results.

This procedure or similar procedure has been recommended by GM over the years for many of their cars.
They recommended Techron.

If this doesn’t cure your problem they will have to replace the sensor/pump located in the right tank.

https://www.autozone.com/deals/dealM...DealMaker=true

Good luck

I had this issue with my c6. Ironically when I filled with sunoco 93 twice.

Put some techron, drove a bit, refilled with shell 93, drove to less than 1/2 tank. Put another bottle of techron and filled back with shell 93.

Gauge fixed itself about 50 miles after that. And problem never came back.

So it could be bad gas.

Thanks guys.
i really appreciate the feedback.
i do drive the car as it has 27000 miles on it. I usually keep it above a half tank except when traveling longer distances.
I’ll try the additives you recommend. I do put fuel additives in about twice a year now but will switch to Techron.

Thanks again.

You also have to remember there are two fuel tanks. The passenger side tank is drained first followed by the driver's side tank. Keeping the fuel level above half tank for long periods means the driver's side fuel level sensor never moves. Keeping fuel level at less than half full for long periods means the passenger side sensor doesn't move. If you run the tank down to empty, add Techron and refill the driver's side tank will have the Techron but the passenger side tank will not have any Techron. Fuel doesn't flow into the passenger side tank until the driver's side is full so you need to put in half of the Techron when the driver side tank is less than full then add the remainder once the fuel level goes above 3/4 so you know the rest of the Techron goes into the passenger side tank.

Bill

If it’s under warranty or you have an extended gmpp bumper to bumper — Sounds like a trip to the dealer is in order when the gauge shows empty and you know you have a near full tank.

FWIW, i have used redline concentrate cleaner in other cars of mine and even in my dad's old 82 toyota pickup and idk if it's placebo but the cars idle smoother and "feels" peppier shortly after putting a bottle of redline.

If you read the reviews on any automotive site, there's a huge praise for redline products. Gear oil, the fuel additive (cleaner) and especially their engine oil since i think it's a TRUE group 5 oil.

You could also have a failed fuel sensor and no amount of additives will resurrect that kind of problem. I had that happen on my C6Z. Gauge started going to zero and then stayed there. It turned out the wiper that wipes a contact across the potentiometer resistor lost the contact creating an open circuit. That required replacing the passenger side fuel level sensor which meant dropping the tank. That isn't an easy job on late C5s, C6s or C7s. It took a short while to get the tank out and the new sensor in but to get the tank back in the car and coupled together with the lines inside the cross over tube took a week. You can't see what you are doing so you are taking a tube with two more tubes inside that move around and trying to mate them with another tube with two matching tubes inside and everything moves around. If you screw up the seal when doing it you have a leak and have to pull everything apart and install new seals. Luckily, I had GMPP and the repair was covered but I watched when the Corvette mechanic with another one helping him initially tried to get it together and found they had a leak. I knew I would have never been able to do that job on the lift in my garage. What an act of frustration getting that thing back together. it does improve your cussing capabilities though.

Bill

i guess this design is good during the factory build process but once the car is built around the tank and something goes wrong it’s pot luck putting it back together.

if the error is in the tanks, then it would have to be in the drivers tank, not passenger tank.

Passenger tank can be empty and car will still read half full if drivers tank is full.

Visa versa, the car will read empty if the drivers tank is empty, even if passenger side is full.... so your problem is in drivers tank, or your problem is outside the tank.

Problem is not inside the passenger tank.

The drivers side level sensor is what has gone bad or come disconnected somehow, is my guess. Hopefully it is outside the tank... but definitely something to have a dealer do if you are under warranty.

If you plan to run bigger HP later, while the drivers tank is out, is the time to add the Fore twin pump hanger for higher HP fueling needs later.

Techron did not fix my Z06. Had to have both fuel sending units replaced under warranty. When issue happens, it throws a code which dealer can read.

Madsen I agree with RobGZ06. This exact thing has happened to me in the past a number of times. 2 or 3 times a year I drive to a town about 100 miles away for an autocross. Typically I would top off the tank at a particular station ( off brand ) when I got there, and then fill again after the events. I found that every time I used gas from that particular station my gas gauge would bounce to empty on the way home. After re-filling locally the problem would soon go away. When I stopped using the off brand gas it never happened again. I agree with others regarding the Techron. Switch gasoline and try a bottle of it before you start throwing real money at the issue.

The odd part for me was that sunoco is on the "top tier gas" list yet it caused me problems.

And the only reason why i filled with sunoco is because the shell station right by my house was having construction done to their entrance/exit. It was still open but the "aprons" to enter and exit was so messed up, basically only SUV's could get through. No way my lowered C6 would have made it.

Been using shell religiously since then (already 4 years now) and never a single problem, with any of my cars.

Shell v-power is the real deal.

where do you live that sunoco is bad so that i can avoid it?

I did some research in the FSM. The info isn't easily found. However, this is what I found. The ECM monitors the fuel level signal coming from both tanks. Unlike previous models the two signals aren't joined electrically. When both tanks are full both sensors read at minimum resistance levels (basically a pot with its wiper output tied back to one end of the pot. With the the wiper all the way to the far end you have max resistance as it approaches the point where the wiper is attached shown in the diagram:
https://cimg8.ibsrv.net/gimg/www.cor...6daee47cc1.png

As the wiper moves to the right the resistance increases as it moves to the left it decreases. I don't show it but there is another resistor that would have be between the right side of pot and ground so the voltage where the wiper is tied can vary up and down. Ground doesn't vary.

These two signals are sent to the ECM as voltage levels. The ECM calculates the fuel level from the signal values and converts it to a digital format that is communicated across the data bus to the Instrument Cluster.

P0461 is set if Fuel Sensor 1 performance is an issue
P0462 is set if Fuel Sensor 1 voltage is low
P0463 is set if Fuel Sensor 1 voltage is high
P0464 is set if Fuel Sensor 1 circuit is intermittent
P2066 is set if Fuel Sensor 2 performance is an issue
P2067 is set if Fuel Sensor 2 voltage is low
P2068 is set if Fuel Sensor 2 voltage is high

If P0464 is set that is a Type A DTC. If any of the others are set the gauge goes to empty. The others are also Type B codes. Type A's set the CEL upon the first failure type B's set it when two consecutive failures occur.

Bill

NJ.

Not sure if sunoco is bad. Maybe it was just wrong timing and the loading truck had a bad tank of gas.

But i filled up twice, 2 weeks apart from each other. Gauge took a crap during my usage of my 2nd fill up of sunoco 93.

That's when i poured techron, and filled the rest of the tank with shell 93.

Who knows if sunoco got better, or there was nothing wrong with it at all. Like i said this was 4 years ago and i NEVER used sunoco again.

Shell 93 vpower in all my cars now.

i stay away from NJ usually so im okay. Just checking.

Thanks for all the input guys. Bill Dearborn THANK YOU�� For the TEC side.
ive taken it to a dealer who said my warranty has expired (more than 36 months old) and I’m on my own on the tank sensors repair.

good news: $126.00 for the part
bad news: $ 2000.00 plus for labor

BTW I use “mostly good fuel but drive a lot from Oregon to Washington to So. California. That means sometimes I don’t get the Best fuels.

thanks agin all

Last time I checked, Sunoco is not a Top Tier gasoline.
I was quite surprised at that.

Sunoco is on the list as Top Tier, click.