Lately my Gas Gauge will just all the sudden drop to Empty and then later on come back up by itself. I already put two bottles of Techron in and run two tanks through it and it doesnt seem to be helping. It only does it ever now and then, think my gauge is bad? Ever since i bought it when i fill up it only goes to 7/8 tank on the gauge so i figured it was the same problem some others have had and the techron fixed it for them but not mine

 

I think after about 2 gallons of Techron, mine is normal. I had given up hope, but learned to reset it with the diagnostics and it would come back online every time.

 

When the gage fails,, without turning the ignition OFF,,,,, read the DTCs and list the Codes that are displayed. It will help narrow down which sensor is causing the issue.

I agree. It may take several doses of techron. Go to AutoZone and see if they have any SEAFOAM. Add the correct amount of SEAFOAM to the next tank and see if that helps. If not, after you run tht tank out, switch back to techron.

READING YOUR C5 Engine Diagnostic Trouble Codes (DTC)

This procedure should be carried out any time you experience a problem with your C5. Most inexpensive store bought aftermarket code readers will ONLY read power train DTC’s. Reading the DTC’s with the C5 built in code reader will allow you to read ALL the modules in the vehicle.

The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold the OPTIONS button
4) While holding OPTIONS, press FUEL button four times within a 10 -second period.

Initially, the on-board diagnostics go into an Automatic Mode which will cycle through each module and shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each module. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.

There are two types of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current code indicates a malfunction is present in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes. More likely it's an indication of an intermittent malfunction.

Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.

Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except E/M. Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press RESET To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles. There are a few body module DTC’s that if set will prevent the module from operating properly. Once the DTC is cleared, the module will return to full function. This is not true for power train DTCs.

If you have never read and cleared your codes, there will probably be a lot of old history DTCs. It is recommended that you clear your codes and see if any come back during a driving cycle. Those are the ones that you need to concentrate on diagnosing.

Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5.

NOTE and a WARNING. You can read the DTCs while the engine is running. I pull mine up all the time while driving.
WARNING. Don’t become distracted while reading DTCs while your driving and cause an accident!!!!! Use common sense and drive safe.

These are some very good C5 Diagnostic Trouble Code (DTC) explanation web sites!!! They also explain how to read the DTCs

Here are some very good sites that explain what DTC mean:

http://www.gearchatter.com/viewtopic11755.php

http://www.obd-codes.com/trouble_cod...d-ii-codes.php

Make sure to include the H or C suffix when you post your DTCs!!

NOTE!!! Start the car and let it idle. Then take it for a drive and cause the problem to occur. When you return home pull the codes BEFORE you shut off the engine.


Do NOT discount the codes with the H following them. They can provide an audit trail for issues going on with the car. They ARE important in diagnosing problems.

Post ALL the codes that you pull with the engine running..........

Some codes go away WITHOUT setting an H code when you shut the engine off. I suspect you will have several codes that will show C or HC that do NOT show when the engine is turned off.

 

After you read the codes and write them down, CLEAR the codes and see if that allows the gage to read normaly.

 

This would always bring mine back to normal.

 

Ok sure will thanks guys

 

I had sender replaced and the condition returned. Several bottles of Techron OR Seafoam and several tankfuls of non-junk high sulpher gas should get it working again. Don't be surprised if it happens again. I have about 8 bottles of Techron in the garage ready for future zero readings.

 

I also had intermittent problems with the fuel quantity gauge. Adding Techron several times seemed to help at first then seemed to make it worse.

Then I read on here that someone recommended letting the car run down to a couple gallons and then putting in about 8 to 9 gallons of gas before quickly adding the big Techron bottle and then finishing the fill up.

The apparent objective is to try and get as much of the Techron as possible into the second tank. After two such treatments, all the problems have gone away for the last six months.

FWIW, I make no pretense that this technique really works. Perhaps using Techron in those five successive fill ups might have solved the problems anyway no matter at what point I actually added the Techron.

 

Just had this happen to me. Car fills up and only shows 7/8 then about 30 miles drops to zero. Fun times. Techron/ seafoam here I come

 

Thanks!

 

Got Techron and Seafoam. Gauge is working well now naturally right... I Just let car hit about half tank then added a bottle of techron and filled with shell gas. Likely going to try Seafoam on next tank. Plan to run this tank pretty low with techron then add half seafoam and put in about 8 gallons then add rest of seafoam and fill the rest up.

I'll see how well this works for me and continue to use Shell Gas.

 

I should invest in techron as much as I put in. My gage goes to zero very predictable. Right at 29/30 miles it goes south. When I fill it up the gage goes past full and will stay there for about 60 miles, then quickly go between 3/4 and 7/8. That's when the 30 mile zero is predicted. My code is 1431indicating my right sending unit is faulty. I'm going to replace it when I get the gas below 1/4. I will let you know what that plays out.

 

I swear I put gallons of techron through mine, but is working fine now, finally! Good luck!

 

FYI

Advance, Autozone, Oreily all seem to have large bottle for $12.99.

You can order online at advance and pick up in store.

Promo code P20 will save you 20% on entire order so each bottle is $10.39.

Other codes

http://www.retailmenot.com/view/advanceautoparts.com

http://www.coupons.com/coupon-codes/advance-auto-parts/

- Educated consumer

 

I'm experiencing the same problem on my 2002. It happened several times and each time the gas gauge would re-set itself....sort of. Finally, I took it back to my dealer, who in turn had to take it to a Chevy dealer because the codes were not available to independent dealers (?). Either way, they fixed the problem. But several days later on the next tank full of gas it happened again. The "Check Gauges" light comes on the dash at the same time.

Are these the same symptoms others on this thread have experienced?

Thanks,
Doug

 

Yes, that's how it goes. I got so I could reset it using the OBD while driving, but keep ur eyes on the road!!

 

The OBD only re-sets the "Low Fuel" warning that comes on. It does not re-set the actual fuel gauge......at least in my case.

 

Reviving a 4-year old thread, Doug...

You're correct; clearing codes will not reset the gauge.

As I recall, this was the topic of a recall many years ago. Don't quote me on the exact details, but the C5 has 2 fuel tanks, each with a separate fuel sender. There's also a pump who's purpose is to keep these 2 tanks essentially even. When the signals from the 2 senders are different enough to exceed a certain threshold, the dash gauge is commanded to read empty. The recall was essentially a software update to allow for a greater differential, but since I experienced this problem under warranty, my senders were replaced as well.

There are essentially 2 reasons for the senders to be inconsistent: either there's a problem in the pump and plumbing between the tanks, or there's a problem with the senders. If you're lucky, it's the latter and not the former, as the plumbing between the tanks has been discontinued, and it's an expensive fix, assuming you can find used parts.

As described on this forum, sulphur in the fuel has been implicated in causing the senders to fail, or at least give inconsistent readings. I just recently had this issue after more than 15 years since the recall was performed. It coincided with 2 consecutive fill-ups at Arco gas stations (which may be coincidental, but I'm betting not and staying clear of Arco). When I poured a can of SeaFoam into the tank in the auto parts store parking lot and started the car, the gauges swept as usual, and the fuel gauge returned to "E". But before I got out of the parking lot, the gauge was back. I'm usually skeptical of snake oils like SeaFoam or Marvel Mystery Oil, but in my case, it's hard to think this was coincidence.

Try a can of SeaFoam. It's about $11 for a can.

 

I never had the gauge issue but shortly after purchasing my C5 3 years ago, I read about the problem on CF and decided to use only Shell Premium. Then I put in a can of Techron at every other fill up. This may be overkill but I am hoping this keeps the issue from appearing.

 

Not true in my case. My gauge would always pop right back up to where it quit. About 1/3 tank usually.