My c5 just started to show inaccurate reading. With ignition on, it reads 3/4, when .moving drops to 1/2. When filled up, the guage only goes to 3/4. What do I do?

 

Very common prob. Start adding Techron concentrate for a few fill ups, the large bottle 1st time. It usually takes care of the problem. The sulphur in the gas contaminates the sensors. I add a small bottle every other fill up & it seems to keep the problem away.

 

needs to be part of your maintanence routine.

 

I think you`re probably right. But since I`m a bit forgetful these days If I remember to add a bottle every 3rd or 4th tank I`m doing good!

 

Thanks for the advice. Chev dealer suggests not using additives, and only to use top tier gas. All I want to do is to have a gas guage that works. Why is everything so complicated? Top tier like Shell, Chevron..any others? I've been using Sunoco, 93 octane....it's convenient , right here on the corner....so much for that, right?

 

I use Chevron Supreme exclusively in the Vette,still had to add a large jug of Techron a few weeks ago when the gauge stuck on "full".
2 days later the gauge was working fine again.

Like 8VETTE7 said-it sounds like the dealer just wants to lighten your wallet by 5 or 6 hundred bucks- and a few years down the road,you could end up with the same problem.
Just dump the Techron in there,let it do it's thing,and all will be as it should be once again.

 

Would this kick out a p0463 code?? glassman74

 

8Vette7,
Do you know what they are for a 98???? Thanks. glassman74

 

DTC P0463 Fuel Level Sensor Circuit High Voltage




Circuit Description
The left Fuel Level sensor, mounted in the rear side of the left fuel tank, measures fuel level changes within the left fuel tank. The left Fuel Level Sensor changes resistance based on fuel level. The Fuel Level Sensor has a signal circuit and a ground circuit. The PCM applies a voltage (about 5.0 volts) on the signal circuit to the sensor. The PCM monitors changes in this voltage caused by changes in the resistance of the sensor to determine fuel level.

When the fuel tank is full, the sensor resistance is high, and the PCMs signal voltage is only pulled down a small amount through the sensor to ground. Therefore, the PCM will sense a high signal voltage (fuel tank full). When the fuel tank is empty, the sensor resistance is low, and the signal voltage is pulled down a greater amount. This causes the PCM to sense a low signal voltage (fuel tank empty).

The PCM uses inputs from the Fuel Level Sensor to calculate the total fuel remaining in the fuel tank(s). This information is then sent to the fuel gauge.

When the PCM senses a signal voltage higher than the normal operating range of the sensor, this DTC sets.

The following is a description on how the fuel pump/system functions: An electric high pressure fuel pump attaches to the fuel sender assembly inside the left fuel tank. The fuel pump pumps fuel to the fuel rail assembly at a specified flow and pressure. Excess fuel from the fuel rail assembly returns to the left fuel tank through the return pipe. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions and aggressive vehicle maneuvers. The PCM controls the electric fuel pump operation through a fuel pump relay.

The left tank fuel pump also supplies a small amount of pressurized fuel to the right fuel tank siphon jet pump through the fuel feed rear crossover pipe. The pressurized fuel creates a venturi action inside the siphon jet pump. The venturi action causes the fuel to be drawn out of the right fuel tank. Fuel is then transferred from the right fuel tank to the left fuel tank through the fuel sender fuel feed pipe. The fuel system is designed to maintain a greater level in the left fuel tank then the right fuel tank when the electric fuel pump is operating. The fuel transfer rate from the left fuel tank to the right fuel tank is less than the transfer rate from the right fuel tank to the left fuel tank. Therefore, with the electric fuel pump operating, the left fuel tank level should be higher than the right fuel tank level.

The fuel level in the fuel tanks equalize when the following occur:

The electric fuel pump is not operating.
The fuel level is greater than 50%.
Conditions for Running the DTC
Engine Running

Conditions for Setting the DTC
Fuel Level Sensor voltage is above 2.9 volts
Conditions met for 50 seconds
Action Taken When the DTC Sets
The powertrain control module (PCM) stores the DTC information into memory when the diagnostic runs and fails.
The malfunction indicator lamp (MIL) will not illuminate.
The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.
Conditions for Clearing the DTC
A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Use a scan tool in order to clear the DTC.
Diagnostic Aids

Important
The PCM terminals C1-24 and C2-24 are the Sensor Ground Jumper terminals. This DTC sets if the jumper is open or the connection between the jumper and the PCM is faulty. Inspect for proper terminal tension/connections at the PCM harness connector before replacing the PCM.
Depending on the current fuel level, it may be difficult to locate a malfunctioning sending unit. The malfunction may only occur when the fuel level is full or near empty. The fuel sending unit may need to be removed for further diagnosis. A Fuel Level sensor that has an intermittent condition causes this DTC to set. Remove the Fuel Level sensor refer to Fuel Sender Assembly Replacement in order to check the resistance of the sensor. The resistance of the sensor should change smoothly from 40ohms to 250ohms. Replace the sensor if the resistance did not change smoothly or was out of range.
Remove any debris from the PCM\TAC module connector surfaces before servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM\TAC modules.

The voltages in the Fuel Level Conversion Table are approximate values. Use this table to aid in diagnosis.

Fuel Level Conversion Table

Approximate Values

Fuel Level
Left Tank voltage
Right Tank Voltage

100 %
2.5 V
2.5 V

75 %
2.5 V
1.5 V

50 %
2.5 V
Less than 1.0 V

25 %
1.7 V
Less than 1.0 V

0 %
Less than 1.0 V
Less than 1.0 V


The following occurs with this DTC set:

The vehicle fuel gauge displays empty.
The Check Gauge lamp illuminates.
The Driver Information Center displays a message.
Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.

 

Thanks! And, where do I buy the Techron and it should be the concentrate?

 

Your local auto parts / accessories store should have some in stock.

I like the Techron concentrate 20oz bottle... drop one in the tank every couple of k miles... no gauge problems so far.

It's small insurance $ when you think about it.

This is so good it may clear up your problem after a couple of applications. Good luck.

Bob

 

I have had this same issue with my Z06. When full it shows 3/4 f and it also shows E with plenty of fuel left in the tank (I can tell because when filling from E to F it takes nowhere near the full tank volume). The guage will also randomly fail while driving and I have to clear the code to make it operational again. I have put at least 10 Techron bottles through it back to back when filling it up. If the problem has existed for a while could it take quite a while to clean it up? Is the techron solution usually something that shows results fast?

 

Just a short note/FYI:

Advance Auto Parts here in Florida has the 20oz easy pour bottle of Techron Concentrate on sale for a whopping $7.00 (regular retail $12)... not too shabby.

Bob

 

Has it ever been found to be an electrical problem? bad ground etc?