fuel gauge ohms

[johnmaster]

Any idea what ohm range my 99 chevy silverado fuel gauge was designed to read? Sender is aftermarket and full on sender is showing 1/8th tank on truck gauge. Running cos5.

[Taz]

... Any idea what ohm range my 99 chevy silverado fuel gauge was designed to read? ...

Hello John,

Your fuel gage sender Ohms range should be 240 to 33 Ohms (empty - full).


Regards,
Taz

[johnmaster]

Thank you!

[johnmaster]

I installed an aftermarket sender for that ohm range, still doesn't work just right.

Full tank reads about 3/4 on vehicle
3/4 tank reads 3/4 on vehicle
1/2 tank reads about right
1/4 tank reads empty on vehicle
empty tank reads empty.

I changed the fuel gauge calibration F0501 table a handful of different ways including all max value and all to min value and it doesn't change the reading at all. Any way to adjust for this weird sender?

[Taz]

Hello John,

What is the capacity of the fuel tank ? (litres / US gallons / Imperial gallons - whichever value you are certain is the maximum capacity).

Post your tune - will take a look ... sometimes a second set of eyes is helpful.


Regards,
Taz

[johnmaster]

It's a propane tank, 50 gallon, the sender should be roughly proportionate to a GM vehicle as it's specified for a GM of that ohm range. Even if i check the ohms at various levels, not sure how to change to accomodate it if the F0501 table doesn't do anything. I've had it at stock 99 chevy numbers, all 200% and all -200% and the needle in the truck doesn't flinch. Not sure if there is some other way to manipulate it or not.

[Taz]

... It's a propane tank, 50 gallon ...

50 US gallons is approximately equal to 189 litres. Make sure whichever units you are working in (gallons or litres) you enter this in F0502 & F0504. This volume 50 / 189 should also be entered in F0507 as the maximum value (generally a few cells prior to 150 - if F0506 is set to 150).



... Not sure if there is some other way to manipulate it or not ...

F0502, F0504, F0506, F0507.

Have you confirmed the empty / half / full ohms output of the sender in the propane tank - or are you simply inferring the output should be the same as the OEM gasoline tank ?


Regards,
Taz

[johnmaster]

Inferring that the sender mfg maker would calibrate their ohm readings to roughly what the production senders put out so they match up at least close. Not sure how the gallons/liters would affect it but i am willing to try, I'll see if that changes anything. without stabbing the harness to read ohms I can't easily get at the wiring, nor the stock tank sender to try to see if they are indeed way off from each other.

Even though my table was not zeroed out could this be a reason why my changes don't do anything?
"If this table is zeroed in your stock tune then assume the PCM does not control the fuel gauge via pulse width modulation.
It may be done via the serial data bus instead."

[Taz]

Hello John,

You never posted a tune - not sure which year / platform you are working with. Yes - fuel gauge information from the PCM to IPC is often via Serial Data. Truck tunes may have F0501 populated - but the PCM will not use this information (as they use Serial Data).


Regards,
Taz

[johnmaster]

Hello John,

You never posted a tune - not sure which year / platform you are working with. Yes - fuel gauge information from the PCM to IPC is often via Serial Data. Truck tunes may have F0501 populated - but the PCM will not use this information (as they use Serial Data).


Regards,
TazSorry, current tune is stuck in my crappy laptop, would need to transfer it from pc to pc to get it up here. Regardless it sounds like there is no way to edit the way the gauge reads if it ignores that table? Or is there? 99 chevy silverado with cos5, used an 02 tune from the file depot as the base.

[Taz]

Hello John,

You will need to measure the exact ohm output of your tank / sender combination - at empty, 1/4, 1/2, 3/4, and full. Then adjust F0507 - such that the PCM will accurately calculate the fuel gauge output sent via Serial Data to the IPC.

F0507 settings may take some trial and error - A/D values appear to be the inverse of the sender ohm output - not sure. Your tank and sender combination are non-OEM, so you will probably have to develop a custom calibration.


Regards,
Taz

[johnmaster]

I tried adjusting the values slightly, than I went extreme to try to get a reaction and nothing I do to that table will affect the needle function. By putting the values to max or min I was expecting to bury the needle in either direction but it doesn't change and it still works the same as it always did.