Fuel Level?

**Chris@HPTuners** · 01-14-2006

there are two main table types:

1. the fuel volume vs. sender input (note, i accidently labelled this axis wrong it seems as %). This table tells the PCM how many liters/gallons of fuel you have remaining based on the input in "AD counts" from the fuel sender. IN vehciles where the cluster communicates with the PCM via the class2 bus this table also specifies the gauge calibration. In later vehicles there are actually 4 tables for this.

2. the other table is the fuel gauge output PWM control, for gauges that are directly wired to the PCM (ie. not class2). Changing this table will affect the signal sent to the gauge based on the % remaining fuel, ie. the fuel volume divided by the fuel tank size.

The calibration of these things depends on the relationship between the sender output and how much fuel is in your tank, this depends on the shape of the tank and the response of the sender. This is why the curve is a little funky cos rarely a fuel tank is a nice square or rectangle shape.

You can log "Fuel Tank Level Sensor (V,V)" which is the sensor voltage ( multiply by 51 to convert to AD counts). Also the "Fuel Tank Level" which is the volume of fuel in the tank from this table.

The % remaining is then a simple divison by the capacity.

Chris...

**mtcrusan** · 01-15-2006

If this all works out would you all make it available for all makes?

**S2H** · 01-15-2006

IF one of you guys runs out of gas because you recalibrated wrong...

I am so gonna laugh my ass off..LOL

**chrisj6** · 01-15-2006

Originally Posted by soundengineer

IF one of you guys runs out of gas because you recalibrated wrong...

I am so gonna laugh my ass off..LOL

I filled up w/gas just for that reason!

Chris

**MeentSS02** · 01-15-2006

Originally Posted by soundengineer

IF one of you guys runs out of gas because you recalibrated wrong...

I am so gonna laugh my ass off..LOL

Where's the "Screw You" smilie?

LOL...

*Edited*

Alright...now that I have some decent information, I'll go back and look at this. Just by trial and error I was able to figure out how to get my gauge to read "F" when it is actually full. As far as the gauge goes, it looks like I have been able to eliminate the rest of the gauge swing (since it goes well past "F" when it is full) by setting the fuel tank capacity at 16.8 20 points higher than the factory setting (the sender input of 130 is technically where full is [2.53 volts * 51], but I don't want my gauge sweeping all the way to the right...I want it on "F" when it is full, and to drop from there, so 16.8 gallons now corresponds to a sender input of 150). So I'm guessing that 0 will need to be shifted 20 points to the right as well so when it is on E, it is no kidding empty.

Now for the fun part...logging data each time I go to fill up with gas to see how much it is saying is there vs. how much it actually takes to fill it up.

Anyone have a good pic of the 1999-2002 fuel tank so I can get an idea of what I'm looking at for a profile since I know this won't be linear?

**MeentSS02** · 01-15-2006

Oh, and I assume my car communicates by the class 2 bus since modifying the fuel volume vs. sender input changed how my gauge operates?

**MeentSS02** · 01-15-2006

And before I forget, is there any reason why my "Fuel Tank Level" PID in the scanner always reads 0? Bug? Fuel Tank Capacity reads just as it should, and the voltage is correct too.

**chrisj6** · 01-15-2006

mine reads either 0.2 or 0.4 gal. Not sure why, it reads fine on autotap.

Chris

**MeentSS02** · 01-16-2006

Hmmmmmm...sounds like it could be a little glitch in the software. Might not be looking in the right spot for the message.

Okay, now for another request:

On 1999-2002 F-bodies, it is a common complaint that our ECT gauges are essentially dummy gauges (they read 210*F from about 180-230 actual ECT). Since I can manipulate my fuel gauge with the PCM, can I do the same with the ECT gauge? Or is it not controlled by the PCM?

**S2H** · 01-16-2006

its only a dummy between 190ish and 220 ish....
mine seems to read pretty acurate at any other temp...of course...I could just be lucky too..LOL

**chrisj6** · 01-16-2006

mine runs at 174 and reads 185*.

Chris

**S2H** · 01-16-2006

maybe I'm lucky then..LOL

**chrisj6** · 01-16-2006

Originally Posted by soundengineer

maybe I'm lucky then..LOL

yeah yeah rub it in!

Chris

**bmfcamaro** · 01-19-2006

hope you guys get this figured out so we can fix our fuel gauges. the million dollar question, will this be an option for the 98 guys?

**MeentSS02** · 01-19-2006

It is working so far...just doing some data gathering.

**Chris@HPTuners** · 01-22-2006

Originally Posted by bmfcamaro

hope you guys get this figured out so we can fix our fuel gauges. the million dollar question, will this be an option for the 98 guys?

yes, i just added it for 97/98's. Email keith@ to get an update if you want to try it.

**bmfcamaro** · 01-22-2006

Originally Posted by Chris@HPTuners

yes, i just added it for 97/98's. Email keith@ to get an update if you want to try it.

dude your awsome.

**pknowles** · 02-28-2006

2 Q's

1. Is there a value to set at what fuel level the "Check gauges" light comes on? I don't see it.

2. How about allowing us to recalibrate the Engine temp gauge?

**Bill@HPTuners** · 02-28-2006

Originally Posted by pknowles

2 Q's

1. Is there a value to set at what fuel level the "Check gauges" light comes on? I don't see it.

2. How about allowing us to recalibrate the Engine temp gauge?

#2 I would definitly like if its something you guys could provide

**MeentSS02** · 02-28-2006

Double

Didn't think about the "Check Gauges" light though...good point too.

So far with my fuel gauge, it is working well. I have about 5 or 6 different data points, and am confident it is finally getting to be accurate.

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