Spooky 52

For DeeGee: Thanks for all the information. I'm going to try resetting the codes and see what happens. The fuel problem is something other than the sender, in my opinion, because it does not respond to a full tank and is so intermittent. The seat codes are obvious and now that I know what the codes are, I can expect to see them until I can afford to buy a new seat, or at least new rails and motors, etc. I had to make adapter plates out of 1/4" diamond plate that I had in the shop just to get the original seat back in. That was a lot of fun. NOT! It's going to take time to get this thing sorted out but the information that I am getting from guys like you on this forum is extremely helpful and much appreciated.

For rebelheart: The Seafoam worked, or at least appeared to do so, only once. I subsequently went through a total of seven bottles of the stuff and the problem remains intermittently so I don't think that sulpher is the cause here. I appreciate your input. Thanks

flynhi

A write up in an old Corvette Fever recommended GM Vehicle Care Fuel Treatment Plus to clean sulfer.
Is this better than Techron?

DeeGee

No trouble.

Have you tried Techron? Its worked for many of us. There are more complicated issues such as the fuel pump but your symptoms don't sound like the one's I'd expect. but never say never.

If not, you're into changing sensors. I can give you links if you need them.

DeeGee

Never heard much about it here. Techron is formulated to get rid of sulfur which is why its popular.

lucky131969

It's the same thing. Techron with a GM label on it.

flynhi

OK
Thanks.

thatreallyslowc5

I just put in some Techron additive every month or two and my problem has completely gone away in my 97, mine did it a few times a week. Never tried SeaFoam.

01_torch_red_vette

where do you normally find techron. I have seen fuel injector cleaner plenty of places, but nothing actually called techron. mine has started to do the drop to empty at random untill i clear the code

wcsinx

Wal Mart carries it as does Advanced Auto.

C5FORFUN2

Corvette is fine (always used Chevron fuel), but the Silverado has this problem and it is worse when the tank is full. Have started the Techron treatment and it apears to be getting better.

lucky131969

Had the same problem with my Silverado last month. Three doses of techron, and it has stabilized.

3rd_Vette

The COSTCO in my area carries it by the case.. I also use Chevron in all my cars. The cheap "grocery store" gas isn't loaded with the additives Chevron has.. Its worth the extra few cents. In my case, nMy Credit card gives me 5% rebate as long as I use "name brand" gas and not the cheapo grocery store fuel, so Chevron is a real deal in the long run...

DeeGee

Han Solo

My car just started this last week. I put a bottle of STP gas treatment in the first day it happened cause that's all the Chevron Food Mart I stopped at carried. (go figure) I followed up with a bottle of Techron and topped the tank up with Chevron fuel. It has happened twice since then but I'm still on the top half of the tank with the Techron additive.

Autozone did a BOGO on Techron a while back so I had run a bottle of it before I ever had this problem and had the other bottle sitting on my tool box. I also use Chevron Premium fuel most of the time.

Today was the first time I entered the DIC and cleared the code with the car running and it made the gauge come back but the light stayed on till I shut the engine off and restarted it.

Anybody got a link to the reprogram TSB info?

DeeGee

It will not reset until after that ignition cycle so you need a restart before the check engine light goes out. I recommend you give the Techron time to work now particularly as the gauge has come back to life.

Han Solo

The gauge comes back to life the second the code is erased.

I have an older TSB on the subject at home I'll copy in later.

Han Solo

Well mine has gone a couple of days without turning on the check gauges light so hopefully it will stay good.

This is the service info I mentioned above.

Document ID# 1411305
2003 Chevrolet Corvette


--------------------------------------------------------------------------------

Fuel Gauge/Pump Diagnostic Tests - kw 4.6 5.7 01-06-04-022 01-06-04-010A battery cluster display DTC gas inaccurate inoperative instrument intermittent IPC light LH2 LS1 LS6 P0461 P1431 P2636 P2066 #PI00110A - (Dec 9, 2003)
Fuel Gauge/Pump Diagnostic Tests
.

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

Condition/Concern:
There have been past concerns that may result in the PCM commanding the fuel gauge to empty or the vehicle running out of fuel without using all the fuel in the tanks. As solutions have been identified, they have been addressed in service bulletins. Service Manual diagnostics and Service Bulletins should be checked to ensure that the customers concern has been properly diagnosed before any repairs are performed. The vehicle may have a concern of the fuel gauge dropping to empty and DTC P1431 (Fuel Level Sensor 2 Performance) present in Corvette and P2636 in the XLR or the vehicle may run out of fuel while still indicating 1/2 tank on the gauge.

The fuel system is designed to use the fuel in the RH (secondary) tank first and then the fuel in the LH (primary) tank. Moving from gage Full to Empty, the RH sender voltage will go from 2.5 volts to 0.7 volts, then the LH sender will go from 2.5 V to 0.7 V. If at any time the RH sender voltage is higher than 0.8 V while the LH is lower than 2.3V, there is probably a jet pump transfer or stuck float issue. The lack of jet transfer could be due to the lack of system pressure or a clogged or inefficient jet pump. This should be determined prior to servicing to avoid replacing the incorrect part. When the fuel gauge is indicating approximately half full/empty or lower, the left hand tank will be full and the right hand tank will be empty under normal operating conditions. When reading the Tech 2 data in the PCM, the sensors must indicate the appropriate fuel level for the PCM to correctly display the actual fuel level accurately.

The following information can be used to diagnose the fuel transfer process which takes place within the fuel system on these two vehicles.

Note: The 1997 through 2002 and early built 2003 Corvettes (Starting on November 25, 2002 with vehicle identification number 35111542, all Corvettes and all 2004 XLR use the FFS fuel system) without the FFS system did not have a secondary regulator which prevents the siphoning of fuel (LH to RH) after the vehicle is turned off. The siphoning could balance the fuel such that, at start-up, the sender voltages could be similar. That is why there is a 40 minute timer on the P1431 DTC on these vehicles to allow the fuel to transfer to the LH tank after start-up.

Recommendation/Instructions:
Fuel Gauge/Clogged Jet Pump Diagnostic Tests

Diagnostic Test Option A:

Add enough fuel to ensure fuel gage level is at approximately three quarters (¾) full.
With Tech 2, check for and record Diagnostic Trouble Codes (DTCs), and monitor fuel level sensors for both tanks for remainder of procedure.
Start vehicle. Run vehicle long enough to confirm RH fuel level decreases while LH remains full (2.5 V).
Diagnostic Test Option B (Draining Fuel):

With Tech 2, check for and record Diagnostic Trouble Codes (DTCs) and monitor fuel level sensors for both tanks for remainder of procedure.
If RH level is greater than 0.8 V while LH level is less than 2.4 V, there may be a jet transfer issue - continue procedure to confirm issue.
Add enough fuel to ensure fuel gage level is approximately three quarters (¾) full.
Install Kent-Moore pressure gage/ drain hose to Schrader valve at fuel rail with drain valve closed.
Start car and verify pressure is 55-60 psi. If pressure is not at this level correct as necessary.
Open drain valve, and drain fuel from rail into empty 5-gallon container. The gage pressure should be @30 psi.
Drain fuel. Monitor both level sensors. Drain until RH sensor level drops 0.15V or more. Verify that LH stays at 2.5V while RH decreases. If RH sensor does not move and LH level sensor decreases, increase gage pressure to 55 psi by closing the drain valve. See if RH sensor starts to decrease. If not, there is a jet transfer issue that needs to be resolved.
With vehicle/fuel pump still running, close drain valve, and verify system rail pressure returns to 55-60 psi.
Shut off vehicle, remove Kent-Moore tool and verify Schrader valve has fully closed. (Key-on vehicle to verify). Replace Schrader cap.
Note: The right side tank sending unit on known good vehicles has shown to be as low as .65 volts while problem vehicles have shown to be above 0.8 volts with the fuel level below a half a tank of fuel (measured).

Replace/repair components as required. Possible causes:

SI should be followed to determine the root cause. If the fuel gage is intermittent or dropped to empty due to a fuel system issue, there should be a DTC set. Follow SI symptom diagnostics for DTC.

1997 - 2003 without the FFS system -

If the fuel pump does not generate the required pressure (about 52 psi) to run the RH jet pump, the system should be evaluated for internal leaks or faulty regulator(s). The source of an internal leak could be a missing or cut o-ring, a loose connection, or a displaced regulator retaining clip. The fuel feed hose that is installed on the left tank (center hose on the left sending unit) feeds the fuel filter and the orifice hose that goes to the right tank. During assembly the Brown fuel feed hose O-ring may have been cut (this is the 2nd O-ring just inside the hose) and the pieces may have plugged the 0.030 orifice. If this occurs there will be no feed into the right tank and therefore the jet pump will not work and fuel will not return to the left tank.
The right side tank fuel sending unit is hanging up for some reason. The float and/or arm may be in contact with something within the tank. This is much less likely on the FFS system.
The newest concern relates to the use of reformulated fuels. Many of these fuels have been formulated to reduce their sulfur content. Occasionally, some fuels may contain a small amount of reactive sulfur that attacks the silver tipped sender wiper arm contacts. The silver is being transferred to the card itself resulting in irregular/erratic voltages. While both senders are affected by this concern, it is most likely the right hand sender that sends the incorrect voltage. This occurs because the PCM is expecting to see the voltage signal from the right hand sender remain below 0.7 volts in the empty position. Signals greater than 0.7 volts are not what the PCM expects to see, causing the PCM to command the fuel gauge to the empty position. Replacing the right hand sender will correct this condition until the reactive sulfur attacks the new sender wiper. The time that it takes for this to reoccur can vary anywhere from several days to much longer. The time frame depends on the amount of reactive sulfur in the fuel along with how long the particular tank full of fuel is in the tank. Changing to a different brand of fuel may provide a solution.
For the 2001 - 2002 model year there is a revised service calibration released for this concern. See bulletin 02-06-04-010a for more information.
For vehicles with the FFS system - you may find a connection problem at either the left or the right tank, "O" rings missing or cut at the left or right tank fuel connections of the crossover tube. This will also cause a lower than expected fuel pressure reading under normal operating conditions. The other possibility is that the jet pump itself is plugged. Check the Julian date on the RH fuel tank module. If the Julian date is 25532 or lower and no other cause is found, then the RH module will need to be replaced. The Julian date is printed on top of the sender next to the part number. Once repairs are completed, especially a vehicle with the FFS system, prior to reassembling the vehicle (installing the 3rd member and torque tube), you may want to verify the system is functioning correctly. This may be accomplished by using a Tech 2 to monitor both sending unit readings. With approximately 4 gallons of fuel in both tanks. Use wiring schematic information from SI to install a fused jumper at the fuel pump relay with the key on and monitor fuel transfer from the right to the left tank. Voltage should go down in the right tank as voltage is going up in the right tank. Caution: With the torque tube and rear axle removed, the engine should not be started. Both fuel systems -
The left side sender has a concern that is causing the voltage to remain above the specified value for the required time to set the DTC.
The right side sender is sending erroneous voltage readings to the PCM for some other reason.
.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

Models:
(1997 - 2004 Chevrolet Corvette) and (2004 Cadillac XLR)

SpeedyZ

Another important note many over looks. Be sure you fill up to at least 3/4 full when adding Techron. Other wise the fuel level will be below the sender and won't see much Techron, specially on the right sender.

What I'm saying is don't put a 1/4 bottle of Techron in a 1/4 tank of fuel and expect very good results.

ROCKnROLL

Is it best to put the techron in before you fill-up or after you've filled-up? If I understand the fuel system set-up, before would be better cause it would get in both tanks where as, after, it would just stay in the one tank. Does it make a difference?

LoneStarFRC

Before.