After refueling, my gauge drops to empty and check gauges warning appears. Eventually, it bounces back up to full. I assume this is an indication that the fuel sensor needs to be replaced. Haven't asked the GM dealer for cost to replace yet, just wondering if this is an expensive fix. Mileage is 30k on 2004 Coupe. Doubt this is a DIY.

 

Very common problem. My gas gauge would drop to zero and I could never get more than 11 gallons in the tanks, even if I ran out of gas. Many bottles of Techron didn't help me. I ended having to replace the fuel pump/sending unit/siphon jet on the passenger side. I had a friend who is a GM mechanic who specializes in Corvettes do mine. He also replaced a leaking drivers side rear differential seal. Total cost was about $1,100 including all parts.

 

I had the same symptom. I put in a bottle of Techron about every fourth tank of gas over an extended period. The problem went away after the third bottle, or about 12 tanks of gas.

 

ALL VERY GOOD recommendations!!!

You can pull up the DTCs and they will tell you EXACTLY which sensor is having the issue!! Do it from the drivers seat!!!!!


READING YOUR Engine Diagnostic Codes


The Diagnostic Display Mode is entered with the following procedure:

1) Turn on the ignition but don't start the engine. NOTE! You can read the DTCs with the engine running and or driving down the road but it can distract you. BE careful! Some DTCs clear themselves when you turn the ignition OFF!

2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold OPTIONS
4) While holding OPTIONS, press FUEL four times within a 10-second period.


Initially, on-board diagnostics go into an Automatic Mode which 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. ( 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 kinds of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current C code indicates a malfunction is present and active 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 English/Metric (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 and hold the RESET button 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.
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. You can GOOGLE the DTC and also find information on it.




Here is very good site that explains the DTCs:


http://www.corvette-web-central.com/C5DTCcode.html


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



Make sure to include the H or C suffix!!

 

I just switched to using nothing but Chevron gas, and the problem went away, and never came back. It's been 10 years.

 

Mine has been doing this for about 3 years now.
I started using only top tier fuels and put Techron or SeaFoam in a few times a year. At first I had to drive at least 20 miles before the gauge would start to work again. Now it only takes about 5 miles. Not perfect yet, but, still working and seems to get a little better every year.

 

Mine does this as well...I have a new driver's side sensor and float sitting in the garage waiting to be installed. In my case, the issue is self inflicted...I switched the fuel pump out on the driver's side and I had to manually move the sensor. Now it makes intermittent contact.

I am not looking forward to dropping the tank again...especially with a trans/dif brace in place. that crossover tube is a bitch to get loose without dropping things, but it can be done!

If you search you can find a number of threads with directions on replacing a fuel pump (need to get the pump out to replace the sensor/float), so that should get you started. I think there's a decent youtube video as well, but its been a while since I looked. It is a pain in the *** but it is something that you can do if you can get enough ground clearance under the car and have simple tools. Especially once you see the labor cost estimate to have a shop do it, you may want to do it yourself.

One recommendation if you do it yourself - empty the tank before you drop it...less weight to work with. You can pull the fuel line loose either near the tank where it connects to the hard line that goes up to the torque tube or in the engine bay (need 3/8" (i think) fuel line disconnect tool, which you can get at any auto parts store), use tubing or whatever to connect the disconnected line to a gas can, and hot wire the fuel pump by jumpering across the fuel pump fuse in the engine bay fuse box. Keep an eye on the level of fuel in the gas can so you dont pour gas all over the floor if it overflows and also keep an eye on the fuel flow. You don't want to run the pump dry, so when it tapers off or changes sound pitch, stop it.

 

So what is different about the Chevron gas? Is ethanol fuel the culprit for these issues? I KNOW that ethanol fuel causes issue for me in our supercharged FJ and the Turbo charged 4runners... so, I run only non-ethanol whenever I can get it...

 

Chevron stations here use 10% ethanol too. AFAIK, it's just the Techron content that keeps the sensors clean. It has to do with sulfur content in gas.