fuel gage
Thread Starter
Drifting
Joined: Nov 2014
Posts: 1,979
Likes: 110
From: Switzerland
so i got this fixed, thanks to pk1 in another thread.
i got a base tune with the centri kit that saved a lot of trouble (thanks doug). it turns out it had one flaw, however, the f0507 and f0509 tables vere set to zero (efilive, they define how the ecu converts the sensor signals). the f0501 is also zero which lead me to believe this stuff not being used. i mentioned this on efiliveforum, but nobody noticed apparently. i even remember checking the original tune at one point and i dont know how this escaped me, i probably took a look just at f0501 and concluded they all were not used. this is how lack of dilligence pays off. so after kp1 mentioned adjusting the two tables i checked again and saw them populated in the original tune. well, i copied the tables into my tune and voila, gauge works and the issue that has been haunting me for two years is gone.
btw, the system is set up to disable the gauge only after 125 km. after loading the base tune i spent several weeks tuning (new injectors, sensors etc.) without driving the car much. so after the problem appeared much later i did not associate it with the new tune in any way. i rather thought it was related to the new fuel pump i put in as that was the last change before the problem.
well, anyway, its been an interesting experience how to diagnose a problem.
i got a base tune with the centri kit that saved a lot of trouble (thanks doug). it turns out it had one flaw, however, the f0507 and f0509 tables vere set to zero (efilive, they define how the ecu converts the sensor signals). the f0501 is also zero which lead me to believe this stuff not being used. i mentioned this on efiliveforum, but nobody noticed apparently. i even remember checking the original tune at one point and i dont know how this escaped me, i probably took a look just at f0501 and concluded they all were not used. this is how lack of dilligence pays off. so after kp1 mentioned adjusting the two tables i checked again and saw them populated in the original tune. well, i copied the tables into my tune and voila, gauge works and the issue that has been haunting me for two years is gone.
btw, the system is set up to disable the gauge only after 125 km. after loading the base tune i spent several weeks tuning (new injectors, sensors etc.) without driving the car much. so after the problem appeared much later i did not associate it with the new tune in any way. i rather thought it was related to the new fuel pump i put in as that was the last change before the problem.
well, anyway, its been an interesting experience how to diagnose a problem.
Last edited by romandian; Jun 3, 2017 at 11:21 AM.
Intermediate
Joined: Aug 2013
Posts: 33
Likes: 3
From: san jose ca
This worked for me.
Had the same issue for two days and Techron worked for me. Just FYI.
Advanced
Joined: Aug 2017
Posts: 60
Likes: 6
While doing the diagnostic check on my car, as a result of the fuel gauge suddenly dropping to empty, I received the code "P1431 H C" I understand from doing other research that the "H" indicates it was a past problem that has corrected itself or been fixed. My gas gauge has done this quite a few times and I returned it to the dealer recently and they "fixed" it only to have it happen again.
While I understand what the "H" is for, what does the "C" represent?
BTW.....just prior to me posting this reply/question and prior to me running the diagnostic check my fuel gauge started working again.
Is this a problem that Techron can cure or is it more of a gauge/relay/other issue?
While I understand what the "H" is for, what does the "C" represent?
BTW.....just prior to me posting this reply/question and prior to me running the diagnostic check my fuel gauge started working again.
Is this a problem that Techron can cure or is it more of a gauge/relay/other issue?
Advanced
Joined: Aug 2017
Posts: 60
Likes: 6
H stands for History and C for Current.
Most but not all systems on the C5 that generate codes do so when the engine is running and those codes will usually have a C or HC after them if the codes are pulled while the engine is running. Once the engine is turned off those C codes are changed to H since they cannot be C unless the engine is running. DO NOT discount the significance of H codes when you pull your codes. They are an audit trail of events that have occurred and often require corrective attention.
To pull your codes with the engine running use the RESET button on the dash to clear any messages displayed in the DIC and then pull codes as normal.
The fuel sensors (one in each tank) on the C5 are very prone to oxidation buildup by the chemicals and low sulfur content of some fuels. This prevents accurate reading of voltages on the sensors by the PCM and the PCM sets codes to indicate if the voltage was higher or lower than it should be and which of the sensors (left or right) is experiencing the problem.
Adding a fuel system cleaner like Techron Concentrate Plus or other similar products will dissolve the corrosion build up in most cases. Add a 20 Oz bottle of Techron to a 1/3rd or less full tank and then fill with your favorite premium fuel. If possible let the car sit for several days to let the solution work on the corrosion. Often several treatments are necessary to clear the problem and then retreat once a year as a preventative measure. In very severe cases it can be necessary to replace the sensors.
Most but not all systems on the C5 that generate codes do so when the engine is running and those codes will usually have a C or HC after them if the codes are pulled while the engine is running. Once the engine is turned off those C codes are changed to H since they cannot be C unless the engine is running. DO NOT discount the significance of H codes when you pull your codes. They are an audit trail of events that have occurred and often require corrective attention.
To pull your codes with the engine running use the RESET button on the dash to clear any messages displayed in the DIC and then pull codes as normal.
The fuel sensors (one in each tank) on the C5 are very prone to oxidation buildup by the chemicals and low sulfur content of some fuels. This prevents accurate reading of voltages on the sensors by the PCM and the PCM sets codes to indicate if the voltage was higher or lower than it should be and which of the sensors (left or right) is experiencing the problem.
Adding a fuel system cleaner like Techron Concentrate Plus or other similar products will dissolve the corrosion build up in most cases. Add a 20 Oz bottle of Techron to a 1/3rd or less full tank and then fill with your favorite premium fuel. If possible let the car sit for several days to let the solution work on the corrosion. Often several treatments are necessary to clear the problem and then retreat once a year as a preventative measure. In very severe cases it can be necessary to replace the sensors.
Thanks 8Vette7. That makes sense. The ability to pull up these numbers and find out what they mean from the diagnostic check sure makes troubleshooting much easier.
Glad I stumbled upon the YouTube video showing how to perform it.
