So any guesses, or even better yet, answeres to what code P1431C is?

I think it has something to do with my phantom gas gauge problem.

This is for a 01 coupe, thanks!

-J

 

I have read that there is a new" PCM calibration (16264703) available that may correct this. Some C5 owners have remedied the problem by either using only Chevron gas or mixing in some Techron a couple of tankfuls in a row. You might want to try that first.

Dave

 

I checked TSB'S and if it has a certain number, GM wants you to replace the sending unit with an updated version.

 

Setting Conditions
The fuel tanks over filled.
Fuel level almost empty, then re-fueled with only a few gallons
The Fuel Level sender became un-stuck during refueling
The Fuel Level sender un-stuck on rough road or while turning
Fuel level sender circuit is open or shorted to ground
Engine running, and the PCM detected one of these 3 conditions: With the secondary fuel tank not empty, more than 150 miles have been accumulated and the PCM did not detect that the fuel level in the right fuel tank moved by at least 0.80 gallons. With the secondary fuel tank not empty and the primary fuel tank not full, engine runtime over 60 minutes, that the primary tank did not achieve the top of its range. Observe, after operating the engine for greater than 60 minutes that the fuel in the right fuel tank will transfer to the left fuel tank. With the secondary fuel tank empty and the primary fuel tank full, that the fuel level in both fuel tanks did not change after traveling more than 200 miles. With the secondary fuel tank empty, observe if the primary fuel level decreased after 200 miles. 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 in-tank fuel pump supplies fuel through an in pipe fuel filter/pressure regulator assembly to the fuel rail. The fuel pressure supplied by the fuel pump exceeds the fuel injectors required pressure. The fuel pressure regulator, which is part of the fuel filter assembly, regulates the fuel pressure supplied to the fuel injectors. Excess fuel returns from the fuel filter/regulator, through a separate fuel return pipe, to the left fuel tank. 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 auxiliary fuel feed rear 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 auxiliary fuel return rear 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.
This code sets in 1 Trip(s).


Quote from diagnostics. [8D]

I know it is refferring to dual tanks but the procedure is similar